2026-05-19 04:48:21
Until this past weekend, a contractor for the Cybersecurity & Infrastructure Security Agency (CISA) maintained a public GitHub repository that exposed credentials to several highly privileged AWS GovCloud accounts and a large number of internal CISA systems. Security experts said the public archive included files detailing how CISA builds, tests and deploys software internally, and that it represents one of the most egregious government data leaks in recent history.
On May 15, KrebsOnSecurity heard from Guillaume Valadon, a researcher with the security firm GitGuardian. Valadon’s company constantly scans public code repositories at GitHub and elsewhere for exposed secrets, automatically alerting the offending accounts of any apparent sensitive data exposures. Valadon said he reached out because the owner in this case wasn’t responding and the information exposed was highly sensitive.
A redacted screenshot of the now-defunct “Private CISA” repository maintained by a CISA contractor.
The GitHub repository that Valadon flagged was named “Private-CISA,” and it harbored a vast number of internal CISA/DHS credentials and files, including cloud keys, tokens, plaintext passwords, logs and other sensitive CISA assets.
Valadon said the exposed CISA credentials represent a textbook example of poor security hygiene, noting that the commit logs in the offending GitHub account show that the CISA administrator disabled the default setting in GitHub that blocks users from publishing SSH keys or other secrets in public code repositories.
“Passwords stored in plain text in a csv, backups in git, explicit commands to disable GitHub secrets detection feature,” Valadon wrote in an email. “I honestly believed that it was all fake before analyzing the content deeper. This is indeed the worst leak that I’ve witnessed in my career. It is obviously an individual’s mistake, but I believe that it might reveal internal practices.”
One of the exposed files, titled “importantAWStokens,” included the administrative credentials to three Amazon AWS GovCloud servers. Another file exposed in their public GitHub repository — “AWS-Workspace-Firefox-Passwords.csv” — listed plaintext usernames and passwords for dozens of internal CISA systems. According to Caturegli, those system included one called “LZ-DSO,” which appears short for “Landing Zone DevSecOps,” the agency’s secure code development environment.
Philippe Caturegli, founder of the security consultancy Seralys, said he tested the AWS keys only to see whether they were still valid and to determine which internal systems the exposed accounts could access. Caturegli said the GitHub account that exposed the CISA secrets exhibits a pattern consistent with an individual operator using the repository as a working scratchpad or synchronization mechanism rather than a curated project repository.
“The use of both a CISA-associated email address and a personal email address suggests the repository may have been used across differently configured environments,” Caturegli observed. “The available Git metadata alone does not prove which endpoint or device was used.”
The Private CISA GitHub repo exposed dozens of plaintext credentials for important CISA GovCloud resources.
Caturegli said he validated that the exposed credentials could authenticate to three AWS GovCloud accounts at a high privilege level. He said the archive also includes plain text credentials to CISA’s internal “artifactory” — essentially a repository of all the code packages they are using to build software — and that this would represent a juicy target for malicious attackers looking for ways to maintain a persistent foothold in CISA systems.
“That would be a prime place to move laterally,” he said. “Backdoor in some software packages, and every time they build something new they deploy your backdoor left and right.”
In response to questions, a spokesperson for CISA said the agency is aware of the reported exposure and is continuing to investigate the situation.
“Currently, there is no indication that any sensitive data was compromised as a result of this incident,” the CISA spokesperson wrote. “While we hold our team members to the highest standards of integrity and operational awareness, we are working to ensure additional safeguards are implemented to prevent future occurrences.”
A review of the GitHub account and its exposed passwords show the “Private CISA” repository was maintained by an employee of Nightwing, a government contractor based in Dulles, Va. Nightwing declined to comment, directing inquiries to CISA.
CISA has not responded to questions about the potential duration of the data exposure, but Caturegli said the Private CISA repository was created on November 13, 2025. The contractor’s GitHub account was created back in September 2018.
The GitHub account that included the Private CISA repo was taken offline shortly after both KrebsOnSecurity and Seralys notified CISA about the exposure. But Caturegli said the exposed AWS keys inexplicably continued to remain valid for another 48 hours.
CISA is currently operating with only a fraction of its normal budget and staffing levels. The agency has lost nearly a third of its workforce since the beginning of the second Trump administration, which forced a series of early retirements, buyouts, and resignations across the agency’s various divisions.
The now-defunct Private CISA repo showed the contractor also used easily-guessed passwords for a number of internal resources; for example, many of the credentials used a password consisting of each platform’s name followed by the current year. Caturegli said such practices would constitute a serious security threat for any organization even if those credentials were never exposed externally, noting that threat actors often use key credentials exposed on the internal network to expand their reach after establishing initial access to a targeted system.
“What I suspect happened is [the CISA contractor] was using this GitHub to synchronize files between a work laptop and a home computer, because he has regularly committed to this repo since November 2025,” Caturegli said. “This would be an embarrassing leak for any company, but it’s even more so in this case because it’s CISA.”
2026-05-13 05:46:45
Artificial intelligence platforms may be just as susceptible to social engineering as human beings, but they are proving remarkably good at finding security vulnerabilities in human-made computer code. That reality is on full display this month with some of the more widely-used software makers — including Apple, Google, Microsoft, Mozilla and Oracle — fixing near record volumes of security bugs, and/or quickening the tempo of their patch releases.
As it does on the second Tuesday of every month, Microsoft today released software updates to address at least 118 security vulnerabilities in its various Windows operating systems and other products. Remarkably, this is the first Patch Tuesday in nearly two years that Microsoft is not shipping any fixes to deal with emergency zero-day flaws that are already being exploited. Nor have any of the flaws fixed today been previously disclosed (potentially giving attackers a heads up in how to exploit the weakness).
Sixteen of the vulnerabilities earned Microsoft’s most-dire “critical” label, meaning malware or miscreants could abuse these bugs to seize remote control over a vulnerable Windows device with little or no help from the user. Rapid7 has done much of the heavy lifting in identifying some of the more concerning critical weaknesses this month, including:
May’s Patch Tuesday is a welcome respite from April, which saw Microsoft fix a near-record 167 security flaws. Microsoft was among a few dozen tech giants given access to a “Project Glasswing,” a much-hyped AI capability developed by Anthropic that appears quite effective at unearthing security vulnerabilities in code.
Apple, another early participant in Project Glasswing, typically fixes an average of 20 vulnerabilities each time it ships a security update for iOS devices, said Chris Goettl, vice president of product management at Ivanti. On May 11, Apple shipped updates to address at least 52 vulnerabilities and backported the changes all the way to iPhone 6s and iOS 15.
Last month, Mozilla released Firefox 150, which resolved a whopping 271 vulnerabilities that were reportedly discovered during the Glasswing evaluation.
“Since Firefox 150.0.0 released, they have been on a more aggressive weekly cadence for security updates including the release of Firefox 150.0.3 on May Patch Tuesday resolving between three to five CVEs in each release,” Goettl said.
The software giant Oracle likewise recently increased its patch pace in response to their work with Glasswing. In its most recent quarterly patch update, Oracle addressed at least 450 flaws, including more than 300 fixes for remotely exploitable, unauthenticated flaws. But at the end of April, Oracle announced it was switching to a monthly update cycle for critical security issues.
On May 8, Google started rolling out updates to its Chrome browser that fixed an astonishing 127 security flaws (up from just 30 the previous month). Chrome automagically downloads available security updates, but installing them requires fully restarting the browser.
If you encounter any weirdness applying the updates from Microsoft or any other vendor mentioned here, feel free to sound off in the comments below. Meantime, if you haven’t backed up your data and/or drive lately, doing that before updating is generally sound advice. For a more granular look at the Microsoft updates released today, checkout this inventory by the SANS Internet Storm Center.
2026-05-08 10:58:46
An ongoing data extortion attack targeting the widely-used education technology platform Canvas disrupted classes and coursework at school districts and universities across the United States today, after a cybercrime group defaced the service’s login page with a ransom demand that threatened to leak data from 275 million students and faculty across nearly 9,000 educational institutions.
A screenshot shared by a reader showing the extortion message that was shown on the Canvas login page today.
Canvas parent firm Instructure responded to today’s defacement attacks by disabling the platform, which is used by thousands of schools, universities and businesses to manage coursework and assignments, and to communicate with students.
Instructure acknowledged a data breach earlier this week, after the cybercrime group ShinyHunters claimed responsibility and said they would leak data on tens of millions of students and faculty unless paid a ransom. The stated deadline for payment was initially set at May 6, but it was later pushed back to May 12.
In a statement on May 6, Instructure said the investigation so far shows the stolen information includes “certain identifying information of users at affected institutions, such as names, email addresses, and student ID numbers, as well as as messages among users.” The company said it found no evidence the breached data included more sensitive information, such as passwords, dates of birth, government identifiers or financial information.
The May 6 update stated that Canvas was fully operational, and that Instructure was not seeing any ongoing unauthorized activity on their platform. “At this stage, we believe the incident has been contained,” Instructure wrote.
However, by mid-day on Thursday, May 7, students and faculty at dozens of schools and universities were flooding social media sites with comments saying that a ransom demand from ShinyHunters had replaced the usual Canvas login page. Instructure responded by pulling Canvas offline and replacing the portal with the message, “Canvas is currently undergoing scheduled maintenance. Check back soon.”
“We anticipate being up soon, and will provide updates as soon as possible,” reads the current message on Instructure’s status page.
While the data stolen by ShinyHunters may or may not contain particularly sensitive information (ShinyHunters claims it includes several billion private messages among students and teachers, as well as names, phone numbers and email addresses), this attack could hardly have come at a worse time for Instructure: Many of the affected schools and universities are in the middle of final exams, and a prolonged outage could be highly damaging for the company.
The extortion message that greeted countless Canvas users today advised the affected schools to negotiate their own ransom payments to prevent the publication of their data — regardless of whether Instructure decides to pay.
“ShinyHunters has breached Instructure (again),” the extortion message read. “Instead of contacting us to resolve it they ignored us and did some ‘security patches.'”
A source close to the investigation who was not authorized to speak to the press told KrebsOnSecurity that a number of universities have already approached the cybercrime group about paying. The same source also pointed out that the ShinyHunters data leak blog no longer lists Instructure among its current extortion victims, and that the samples of data stolen from Canvas customers were removed as well. Data extortion groups like ShinyHunters will typically only remove victims from their leak sites after receiving an extortion payment or after a victim agrees to negotiate.
Dipan Mann, founder and CEO of the security firm Cloudskope, slammed Instructure for referring to today’s outage as a “scheduled maintenance” event on its status page. Mann said Shiny Hunters first demonstrated they’d breached Instructure on May 1, prompting Instructure’s Chief Information Security Officer Steve Proud to declare the following day that the incident had been contained. But Mann said today’s attack is at least the third time in the past eight months that Instructure has been breached by ShinyHunters.
In a blog post today, Mann noted that in September 2025, ShinyHunters released thousands of internal University of Pennsylvania files — donor records, internal memos, and other confidential materials — through what the Daily Pennsylvanian and other outlets later determined was, in part, a Canvas/Instructure-mediated access path.
“Penn was the named victim,” Mann wrote. “Instructure was the mechanism. The incident was treated as a Penn-specific story by most of the national press and quietly handled by Instructure as a customer-specific matter. That framing was wrong then. It is dramatically more wrong in light of the May 2026 events, which now look like the planned escalation of an attack pattern that ShinyHunters had been working against Instructure’s environment for at least eight months prior. The September 2025 Penn breach was the proof of concept. The May 1, 2026 incident was the production run. The May 7, 2026 recompromise was ShinyHunters demonstrating publicly that the May 2 ‘containment’ did not happen.”
In February, a ShinyHunters spokesperson told The Daily Pennsylvanian that Penn failed to pay a $1 million ransom demand. On March 5, ShinyHunters published 461 megabytes worth of data stolen from Penn, including thousands of files such as donor records and internal memos.
ShinyHunters is a prolific and fluid cybercriminal group that specializes in data theft and extortion. They typically gain access to companies through voice phishing and social engineering attacks that often involve impersonating IT personnel or other trusted members of a targeted organization.
Last month, ShinyHunters relieved the home security giant ADT of personal information on 5.5 million customers. The extortion group told BleepingComputer they breached the company by compromising an employee’s Okta single sign-on account in a voice phishing attack that enabled access to ADT’s Salesforce instance. BleepingComputer says ShinyHunters recently has taken credit for a number of extortion attacks against high-profile organizations, including Medtronic, Rockstar Games, McGraw Hill, 7-Eleven and the cruise line operator Carnival.
The attack on Canvas customers is just one of several major cybercrime campaigns being launched by ShinyHunters at the moment, said Charles Carmakal, chief technology officer at the Google-owned Mandiant Consulting. Carmakal declined to comment specifically on the Canvas breach, but said “there are multiple concurrent and discrete ShinyHunters intrusion and extortion campaigns happening right now.”
Cloudskope’s Mann said what happens next depends largely on whether Instructure’s customers — the universities, K-12 districts, and education ministries paying for Canvas — choose to apply pressure or absorb the breach quietly.
“The history of education-vendor incidents suggests the path of least resistance is the second one,” he concluded.
Update, May 8, 11:05 a.m. ET: Instructure has published an incident update page that includes more information about the breach. Instructure said its Canvas portal is functioning normally again, and that the hackers exploited an issue related to Free-for-Teacher accounts.
“This is the same issue that led to the unauthorized access the prior week,” Instructure wrote. “As a result, we have made the difficult decision to temporarily shut down Free-for-Teacher accounts. These accounts have been a core part of our platform, and we’re committed to resolving the issues with these accounts.”
Instructure said affected organizations were notified on May 6.
“If your organization is affected, Instructure will contact your organization’s primary contacts directly,” the update states. “Please don’t rely on third-party lists or social media posts naming potentially affected organizations as those lists aren’t verified. Instructure will confirm validated information through direct outreach to all affected organizations.”
Update, May 11, 10:16 p.m. ET: Instructure posted an update saying they paid their extortionists in exchange for a promise to destroy the stolen data. “The data was returned to us,” the update reads. “We received digital confirmation of data destruction (shred logs). We have been informed that no Instructure customers will be extorted as a result of this incident, publicly or otherwise.”
2026-04-30 22:04:26
A Brazilian tech firm that specializes in protecting networks from distributed denial-of-service (DDoS) attacks has been enabling a botnet responsible for an extended campaign of massive DDoS attacks against other network operators in Brazil, KrebsOnSecurity has learned. The firm’s chief executive says the malicious activity resulted from a security breach and was likely the work of a competitor trying to tarnish his company’s public image.
An Archer AX21 router from TP-Link. Image: tp-link.com.
For the past several years, security experts have tracked a series of massive DDoS attacks originating from Brazil and solely targeting Brazilian ISPs. Until recently, it was less than clear who or what was behind these digital sieges. That changed earlier this month when a trusted source who asked to remain anonymous shared a curious file archive that was exposed in an open directory online.
The exposed archive contained several Portuguese-language malicious programs written in Python. It also included the private SSH authentication keys belonging to the CEO of Huge Networks, a Brazilian ISP that primarily offers DDoS protection to other Brazilian network operators.
Founded in Miami, Fla. in 2014, Huge Networks’s operations are centered in Brazil. The company originated from protecting game servers against DDoS attacks and evolved into an ISP-focused DDoS mitigation provider. It does not appear in any public abuse complaints and is not associated with any known DDoS-for-hire services.
Nevertheless, the exposed archive shows that a Brazil-based threat actor maintained root access to Huge Networks infrastructure and built a powerful DDoS botnet by routinely mass-scanning the Internet for insecure Internet routers and unmanaged domain name system (DNS) servers on the Web that could be enlisted in attacks.
DNS is what allows Internet users to reach websites by typing familiar domain names instead of the associated IP addresses. Ideally, DNS servers only provide answers to machines within a trusted domain. But so-called “DNS reflection” attacks rely on DNS servers that are (mis)configured to accept queries from anywhere on the Web. Attackers can send spoofed DNS queries to these servers so that the request appears to come from the target’s network. That way, when the DNS servers respond, they reply to the spoofed (targeted) address.
By taking advantage of an extension to the DNS protocol that enables large DNS messages, botmasters can dramatically boost the size and impact of a reflection attack — crafting DNS queries so that the responses are much bigger than the requests. For example, an attacker could compose a DNS request of less than 100 bytes, prompting a response that is 60-70 times as large. This amplification effect is especially pronounced when the perpetrators can query many DNS servers with these spoofed requests from tens of thousands of compromised devices simultaneously.
A DNS amplification and reflection attack, illustrated. Image: veracara.digicert.com.
The exposed file archive includes a command-line history showing exactly how this attacker built and maintained a powerful botnet by scouring the Internet for TP-Link Archer AX21 routers. Specifically, the botnet seeks out TP-Link devices that remain vulnerable to CVE-2023-1389, an unauthenticated command injection vulnerability that was patched back in April 2023.
Malicious domains in the exposed Python attack scripts included DNS lookups for hikylover[.]st, and c.loyaltyservices[.]lol, both domains that have been flagged in the past year as control servers for an Internet of Things (IoT) botnet powered by a Mirai malware variant.
The leaked archive shows the botmaster coordinated their scanning from a Digital Ocean server that has been flagged for abusive activity hundreds of times in the past year. The Python scripts invoke multiple Internet addresses assigned to Huge Networks that were used to identify targets and execute DDoS campaigns. The attacks were strictly limited to Brazilian IP address ranges, and the scripts show that each selected IP address prefix was attacked for 10-60 seconds with four parallel processes per host before the botnet moved on to the next target.
The archive also shows these malicious Python scripts relied on private SSH keys belonging to Huge Networks’s CEO, Erick Nascimento. Reached for comment about the files, Mr. Nascimento said he did not write the attack programs and that he didn’t realize the extent of the DDoS campaigns until contacted by KrebsOnSecurity.
“We received and notified many Tier 1 upstreams regarding very very large DDoS attacks against small ISPs,” Nascimento said. “We didn’t dig deep enough at the time, and what you sent makes that clear.”
Nascimento said the unauthorized activity is likely related to a digital intrusion first detected in January 2026 that compromised two of the company’s development servers, as well as his personal SSH keys. But he said there’s no evidence those keys were used after January.
“We notified the team in writing the same day, wiped the boxes, and rotated keys,” Nascimento said, sharing a screenshot of a January 11 notification from Digital Ocean. “All documented internally.”
Mr. Nascimento said Huge Networks has since engaged a third-party network forensics firm to investigate further.
“Our working assessment so far is that this all started with a single internal compromise — one pivot point that gave the attacker downstream access to some resources, including a legacy personal droplet of mine,” he wrote.
“The compromise happened through a bastion/jump server that several people had access to,” Nascimento continued. “Digital Ocean flagged the droplet on January 11 — compromised due to a leaked SSH key, in their wording — I was traveling at the time and addressed it on return. That droplet was deprecated and destroyed, and it was never part of Huge Networks infrastructure.”
The malicious software that powers the botnet of TP-Link devices used in the DDoS attacks on Brazilian ISPs is based on Mirai, a malware strain that made its public debut in September 2016 by launching a then record-smashing DDoS attack that kept this website offline for four days. In January 2017, KrebsOnSecurity identified the Mirai authors as the co-owners of a DDoS mitigation firm that was using the botnet to attack gaming servers and scare up new clients.
In May 2025, KrebsOnSecurity was hit by another Mirai-based DDoS that Google called the largest attack it had ever mitigated. That report implicated a 20-something Brazilian man who was running a DDoS mitigation company as well as several DDoS-for-hire services that have since been seized by the FBI.
Nascimento flatly denied being involved in DDoS attacks against Brazilian operators to generate business for his company’s services.
“We don’t run DDoS attacks against Brazilian operators to sell protection,” Nascimento wrote in response to questions. “Our sales model is mostly inbound and through channel integrator, distributors, partners — not active prospecting based on market incidents. The targets in the scripts you received are small regional providers, the vast majority of which are neither in our customer base nor in our commercial pipeline — a fact verifiable through public sources like QRator.”
Nascimento maintains he has “strong evidence stored on the blockchain” that this was all done by a competitor. As for who that competitor might be, the CEO wouldn’t say.
“I would love to share this with you, but it could not be published as it would lose the surprise factor against my dishonest competitor,” he explained. “Coincidentally or not, your contact happened a week before an important event – one that this competitor has NEVER participated in (and it’s a traditional event in the sector). And this year, they will be participating. Strange, isn’t it?”
Strange indeed.
2026-04-21 22:53:59
A 24-year-old British national and senior member of the cybercrime group “Scattered Spider” has pleaded guilty to wire fraud conspiracy and aggravated identity theft. Tyler Robert Buchanan admitted his role in a series of text-message phishing attacks in the summer of 2022 that allowed the group to hack into at least a dozen major technology companies and steal tens of millions of dollars worth of cryptocurrency from investors.
Buchanan’s hacker handle “Tylerb” once graced a leaderboard in the English-language criminal hacking scene that tracked the most accomplished cyber thieves. Now in U.S. custody and awaiting sentencing, the Dundee, Scotland native is facing the possibility of more than 20 years in prison.
Two photos published in a Daily Mail story dated May 3, 2025 show Buchanan as a child (left) and as an adult being detained by airport authorities in Spain. “M&S” in this screenshot refers to Marks & Spencer, a major U.K. retail chain that suffered a ransomware attack last year at the hands of Scattered Spider.
Scattered Spider is the name given to a prolific English-speaking cybercrime group known for using social engineering tactics to break into companies and steal data for ransom, often impersonating employees or contractors to deceive IT help desks into granting access.
As part of his guilty plea, Buchanan admitted conspiring with other Scattered Spider members to launch tens of thousands of SMS-based phishing attacks in 2022 that led to intrusions at a number of technology companies, including Twilio, LastPass, DoorDash, and Mailchimp.
The group then used data stolen in those breaches to carry out SIM-swapping attacks that siphoned funds from individual cryptocurrency investors. In an unauthorized SIM-swap, crooks transfer the target’s phone number to a device they control and intercept any text messages or phone calls to the victim’s device — such as one-time passcodes for authentication and password reset links sent via SMS. The U.S. Justice Department said Buchanan admitted to stealing at least $8 million in virtual currency from individual victims throughout the United States.
FBI investigators tied Buchanan to the 2022 SMS phishing attacks after discovering the same username and email address was used to register numerous phishing domains seen in the campaign. The domain registrar NameCheap found that less than a month before the phishing spree, the account that registered those domains logged in from an Internet address in the U.K. FBI investigators said the Scottish police told them the address was leased to Buchanan throughout 2022.
As first reported by KrebsOnSecurity, Buchanan fled the United Kingdom in February 2023, after a rival cybercrime gang hired thugs to invade his home, assault his mother, and threaten to burn him with a blowtorch unless he gave up the keys to his cryptocurrency wallet. That same year, U.K. investigators found a device at Buchanan’s Scotland residence that included data stolen from SMS phishing victims and seed phrases from cryptocurrency theft victims.
Buchanan was arrested by Spanish authorities in June 2024 while trying to board a flight to Italy. He was extradited to the United States and has remained in U.S. federal custody since April 2025.
Buchanan is the second known Scattered Spider member to plead guilty. Noah Michael Urban, 21, of Palm Coast, Fla., was sentenced to 10 years in federal prison last year and ordered to pay $13 million in restitution. Three other alleged co-conspirators — Ahmed Hossam Eldin Elbadawy, 24, a.k.a. “AD,” of College Station, Texas; Evans Onyeaka Osiebo, 21, of Dallas, Texas; and Joel Martin Evans, 26, a.k.a. “joeleoli,” of Jacksonville, North Carolina – still face criminal charges.
Two other alleged Scattered Spider members will soon be tried in the United Kingdom. Owen Flowers, 18, and Thalha Jubair, 20, are facing charges related to the hacking and extortion of several large U.K. retailers, the London transit system, and healthcare providers in the United States. Both have pleaded not guilty, and their trial is slated to begin in June.
Investigators say the Scattered Spider suspects are part of a sprawling cybercriminal community online known as “The Com,” wherein hackers from different cliques boast publicly on Telegram and Discord about high-profile cyber thefts that almost invariably begin with social engineering — tricking people over the phone, email or SMS into giving away credentials that allow remote access to corporate internal networks.
One of the more popular SIM-swapping channels on Telegram has long maintained a leaderboard of the most rapacious SIM-swappers, indexed by their supposed conquests in stealing cryptocurrency. That leaderboard previously listed Buchanan’s hacker alias Tylerb at #65 (out of 100 hackers), with Urban’s moniker “Sosa” coming in at #24.
Buchanan’s sentencing hearing is scheduled for August 21, 2026. According to the Justice Department, he faces a statutory maximum sentence of 22 years in federal prison. However, any sentence the judge hands down in this case may be significantly tempered by a number of mitigating factors in the U.S. Sentencing Guidelines, including the defendant’s age, criminal history, time already served in U.S. custody, and the degree to which they cooperated with federal authorities.
2026-04-15 05:47:59
Microsoft today pushed software updates to fix a staggering 167 security vulnerabilities in its Windows operating systems and related software, including a SharePoint Server zero-day and a publicly disclosed weakness in Windows Defender dubbed “BlueHammer.” Separately, Google Chrome fixed its fourth zero-day of 2026, and an emergency update for Adobe Reader nixes an actively exploited flaw that can lead to remote code execution.
Redmond warns that attackers are already targeting CVE-2026-32201, a vulnerability in Microsoft SharePoint Server that allows attackers to spoof trusted content or interfaces over a network.
Mike Walters, president and co-founder of Action1, said CVE-2026-32201 can be used to deceive employees, partners, or customers by presenting falsified information within trusted SharePoint environments.
“This CVE can enable phishing attacks, unauthorized data manipulation, or social engineering campaigns that lead to further compromise,” Walters said. “The presence of active exploitation significantly increases organizational risk.”
Microsoft also addressed BlueHammer (CVE-2026-33825), a privilege escalation bug in Windows Defender. According to BleepingComputer, the researcher who discovered the flaw published exploit code for it after notifying Microsoft and growing exasperated with their response. Will Dormann, senior principal vulnerability analyst at Tharros, says he confirmed that the public BlueHammer exploit code no longer works after installing today’s patches.
Satnam Narang, senior staff research engineer at Tenable, said April marks the second-biggest Patch Tuesday ever for Microsoft. Narang also said there are indications that a zero-day flaw Adobe patched in an emergency update on April 11 — CVE-2026-34621 — has seen active exploitation since at least November 2025.
Adam Barnett, lead software engineer at Rapid7, called the patch total from Microsoft today “a new record in that category” because it includes nearly 60 browser vulnerabilities. Barnett said it might be tempting to imagine that this sudden spike was tied to the buzz around the announcement a week ago today of Project Glasswing — a much-hyped but still unreleased new AI capability from Anthropic that is reportedly quite good at finding bugs in a vast array of software.
But he notes that Microsoft Edge is based on the Chromium engine, and the Chromium maintainers acknowledge a wide range of researchers for the vulnerabilities which Microsoft republished last Friday.
“A safe conclusion is that this increase in volume is driven by ever-expanding AI capabilities,” Barnett said. “We should expect to see further increases in vulnerability reporting volume as the impact of AI models extend further, both in terms of capability and availability.”
Finally, no matter what browser you use to surf the web, it’s important to completely close out and restart the browser periodically. This is really easy to put off (especially if you have a bajillion tabs open at any time) but it’s the only way to ensure that any available updates get installed. For example, a Google Chrome update released earlier this month fixed 21 security holes, including the high-severity zero-day flaw CVE-2026-5281.
For a clickable, per-patch breakdown, check out the SANS Internet Storm Center Patch Tuesday roundup. Running into problems applying any of these updates? Leave a note about it in the comments below and there’s a decent chance someone here will pipe in with a solution.