Microsoft today released updates to plug at least 121 security holes in its Windows operating systems and software, including one vulnerability that is already being exploited in the wild. Eleven of those flaws earned Microsoft’s most-dire “critical” rating, meaning malware or malcontents could exploit them with little to no interaction from Windows users.

The zero-day flaw already seeing exploitation is CVE-2025-29824, a local elevation of privilege bug in the Windows Common Log File System (CLFS) driver.  Microsoft rates it as “important,” but as Chris Goettl from Ivanti points out, risk-based prioritization warrants treating it as critical.

This CLFS component of Windows is no stranger to Patch Tuesday: According to Tenable’s Satnam Narang, since 2022 Microsoft has patched 32 CLFS vulnerabilities — averaging 10 per year — with six of them exploited in the wild. The last CLFS zero-day was patched in December 2024.

Narang notes that while flaws allowing attackers to install arbitrary code are consistently top overall Patch Tuesday features, the data is reversed for zero-day exploitation.

“For the past two years, elevation of privilege flaws have led the pack and, so far in 2025, account for over half of all zero-days exploited,” Narang wrote.

Rapid7’s Adam Barnett warns that any Windows defenders responsible for an LDAP server — which means almost any organization with a non-trivial Microsoft footprint — should add patching for the critical flaw CVE-2025-26663 to their to-do list.

“With no privileges required, no need for user interaction, and code execution presumably in the context of the LDAP server itself, successful exploitation would be an attractive shortcut to any attacker,” Barnett said. “Anyone wondering if today is a re-run of December 2024 Patch Tuesday can take some small solace in the fact that the worst of the trio of LDAP critical RCEs published at the end of last year was likely easier to exploit than today’s example, since today’s CVE-2025-26663 requires that an attacker win a race condition. Despite that, Microsoft still expects that exploitation is more likely.”

Among the critical updates Microsoft patched this month are remote code execution flaws in Windows Remote Desktop services (RDP), including CVE-2025-26671, CVE-2025-27480 and CVE-2025-27482; only the latter two are rated “critical,” and Microsoft marked both of them as “Exploitation More Likely.”

Perhaps the most widespread vulnerabilities fixed this month were in web browsers. Google Chrome updated to fix 13 flaws this week, and Mozilla Firefox fixed eight bugs, with possibly more updates coming later this week for Microsoft Edge.

As it tends to do on Patch Tuesdays, Adobe has released 12 updates resolving 54 security holes across a range of products, including ColdFusion, Adobe Commerce, Experience Manager Forms, After Effects, Media Encoder, Bridge, Premiere Pro, Photoshop, Animate, AEM Screens, and FrameMaker.

Apple users may need to patch as well. On March 31, Apple released a huge security update (more than three gigabytes in size) to fix issues in a range of their products, including at least one zero-day flaw.

And in case you missed it, on March 31, 2025 Apple released a rather large batch of security updates for a wide range of their products, from macOS to the iOS operating systems on iPhones and iPads.

Earlier today, Microsoft included a note saying Windows 10 security updates weren’t available but would be released as soon as possible. It appears from browsing askwoody.com that this snafu has since been rectified. Either way, if you run into complications applying any of these updates please leave a note about it in the comments below, because the chances are good that someone else had the same problem.

As ever, please consider backing up your data and or devices prior to updating, which makes it far less complicated to undo a software update gone awry. For more granular details on today’s Patch Tuesday, check out the SANS Internet Storm Center’s roundup. Microsoft’s update guide for April 2025 is here.

For more details on Patch Tuesday, check out the write-ups from Action1 and Automox.

A clever malware deployment scheme first spotted in targeted attacks last year has now gone mainstream. In this scam, dubbed “ClickFix,” the visitor to a hacked or malicious website is asked to distinguish themselves from bots by pressing a combination of keyboard keys that causes Microsoft Windows to download password-stealing malware.

ClickFix attacks mimic the “Verify You are a Human” tests that many websites use to separate real visitors from content-scraping bots. This particular scam usually starts with a website popup that looks something like this:

Clicking the “I’m not a robot” button generates a pop-up message asking the user to take three sequential steps to prove their humanity.

Step 1 involves simultaneously pressing the keyboard key with the Windows icon and the letter “R,” which opens a Windows “Run” prompt that will execute any specified program that is already installed on the system.

Step 2 asks the user to press the “CTRL” key and the letter “V” at the same time, which pastes malicious code from the site’s virtual clipboard.

Step 3 — pressing the “Enter” key — causes Windows to download and launch malicious code through “mshta.exe,” a Windows program designed to run Microsoft HTML application files.

“This campaign delivers multiple families of commodity malware, including XWorm, Lumma stealer, VenomRAT, AsyncRAT, Danabot, and NetSupport RAT,” Microsoft wrote in a blog post on Thursday. “Depending on the specific payload, the specific code launched through mshta.exe varies. Some samples have downloaded PowerShell, JavaScript, and portable executable (PE) content.”

According to Microsoft, hospitality workers are being tricked into downloading credential-stealing malware by cybercriminals impersonating Booking.com. The company said attackers have been sending malicious emails impersonating Booking.com, often referencing negative guest reviews, requests from prospective guests, or online promotion opportunities — all in a bid to convince people to step through one of these ClickFix attacks.

In November 2024, KrebsOnSecurity reported that hundreds of hotels that use booking.com had been subject to targeted phishing attacks. Some of those lures worked, and allowed thieves to gain control over booking.com accounts. From there, they sent out phishing messages asking for financial information from people who’d just booked travel through the company’s app.

Earlier this month, the security firm Arctic Wolf warned about ClickFix attacks targeting people working in the healthcare sector. The company said those attacks leveraged malicious code stitched into the widely used physical therapy video site HEP2go that redirected visitors to a ClickFix prompt.

An alert (PDF) released in October 2024 by the U.S. Department of Health and Human Services warned that the ClickFix attack can take many forms, including fake Google Chrome error pages and popups that spoof Facebook.

The ClickFix attack — and its reliance on mshta.exe — is reminiscent of phishing techniques employed for years that hid exploits inside Microsoft Office macros. Malicious macros became such a common malware threat that Microsoft was forced to start blocking macros by default in Office documents that try to download content from the web.

Alas, the email security vendor Proofpoint has documented plenty of ClickFix attacks via phishing emails that include HTML attachments spoofing Microsoft Office files. When opened, the attachment displays an image of Microsoft Word document with a pop-up error message directing users to click the “Solution” or “How to Fix” button.

Organizations that wish to do so can take advantage of Microsoft Group Policy restrictions to prevent Windows from executing the “run” command when users hit the Windows key and the “R” key simultaneously.

Brace yourselves... and consider reading your email in plaintext for now