December Patch Tuesday 2025: A Month of AI Upgrades, UX Polish — and a Quiet Fix to a Long-Running Windows Shortcut Flaw

As 2025 draws to a close, Microsoft delivers a December Patch Tuesday that feels both familiar and surprising. Familiar, because we once again see Windows 11 gaining incremental improvements in design, security, and AI. Surprising, because one of the most interesting fixes of the month is a vulnerability Microsoft previously insisted wasn’t worth patching — yet quietly corrected in the background.

This month’s updates revolve around three main topics:

• the KB5070311 preview update,
• the critical servicing stack refresh (KB5071142),
• and the silent fix of the LNK shortcut vulnerability (CVE-2025-9491) that’s been abused for years by state-sponsored attackers.

Let’s break down what changed, why it matters, and what ToolsLib readers should pay attention to.

A Closer Look at KB5070311: Visual Polish and New Login Features for Windows 11

Released on December 1st as a preview update, KB5070311 targets Windows 11 versions 24H2 and 25H2. Preview updates don’t usually make headlines, but this one brings a series of meaningful tweaks — especially for users who spend their days in File Explorer.

A Modernized File Explorer Dark Mode

Dark mode in File Explorer has been inconsistent for years, with mismatched grey tones, outdated dialogs, and UI elements that looked like leftovers from older Windows eras. KB5070311 finally brings much-needed polish: context menus blend properly, dialog boxes adopt a unified design, and even video thumbnails are displayed more cleanly.

These changes won’t revolutionize Windows, but they make daily use more pleasant and less visually jarring — a small quality-of-life improvement that’s been a long time coming.

Better Login Experience: External Fingerprint Reader Support

Another highlight is expanded support for external fingerprint sensors under Windows Hello Enhanced Sign-in Security (ESS). This is especially useful for organizations equipping desktops or laptops without built-in biometric hardware. The login process for newly created user profiles also gets faster, making onboarding smoother across enterprise environments.

The Settings App Slowly Grows Up

Microsoft continues its multi-year project of unifying system settings under a modern interface. In this update:

• Keyboard repeat rate and input delay move into the new Settings UI
• Text cursor options are brought in line with the modern page layouts
• Mobile-device integration is redesigned
• Even the classic “About this PC” page finally loses its outdated look

It’s another step in the long journey of retiring the old Control Panel — though that battle is far from over.

Copilot Gets Smarter (Whether You Asked for It or Not)

Microsoft’s ongoing “Copilot PC” strategy drives more AI deeper into Windows. KB5070311 updates semantic search, image recognition, text extraction, and other AI-powered components. These enhancements allow Copilot to propose more helpful system suggestions, offer clearer explanations when actions are blocked, and improve image search both in Photo Viewer and File Explorer.

AI in Windows is becoming less of an add-on and more of a core system feature. For some users, this is welcome. For others, it feels like Windows is becoming too dependent on AI-driven automation. Whichever side you are on, one thing is clear: the direction is set.

But Not All Is Perfect: Two Known Issues

Microsoft confirmed two bugs introduced in this preview:

1. A bright white flash appears in dark mode File Explorer when opening tabs or switching sections. Very noticeable on OLED screens.
2. The password-input icon on the lock screen sometimes disappears, leaving an invisible but functional field — confusing, and an accessibility problem.

Until Microsoft releases a hotfix, it’s wise to keep KB5070311 away from production machines.

KB5071142: A Crucial but Invisible Update to Windows’ Foundations

Servicing Stack Updates (SSUs) rarely attract attention because they don’t introduce visible features. But they’re fundamental. KB5071142 updates the internal engine that installs future patches. Without it, systems may fail to update correctly, accumulate corrupted components, or fall out of compliance.

Think of it as structural maintenance: invisible, but necessary to keep everything standing.

CVE-2025-9491: The Shortcut File Trick That Microsoft Downplayed — Until They Quietly Fixed It

The most intriguing story this month isn’t part of Patch Tuesday’s official notes at all. It revolves around a vulnerability in Windows shortcut (.lnk) files that’s been exploited actively since at least 2017.

The Problem: What You See Is Not What You Execute

Attackers discovered they could hide a malicious command inside a shortcut by padding the visible part with so much whitespace that users couldn’t see the dangerous segment — even when scrolling. Worse: Windows’ Properties dialog only displayed the first 260 characters of the Target field, even though the real command could be tens of thousands of characters long.

In short:

The shortcut could execute actions the UI never showed you.

Exploitation in the Wild

Security firms including Trend Micro, HarfangLab, and Arctic Wolf observed the flaw being abused by:

• Chinese threat groups (UNC6384),
• XDSpy in Eastern Europe,
• and operators linked to Iran, Russia, and North Korea.

Their goals ranged from espionage to lateral movement and data theft.

Despite this, Microsoft initially insisted the issue did not “meet the bar” for servicing.

The Silent Patch That Appeared Months Later

Then, without fanfare, Windows suddenly began showing the entire Target command — no truncation, no hiding, no CVE mention. Testing showed that this behavior appeared sometime between June and November 2025, depending on system version and update cadence.

Microsoft still hasn’t formally acknowledged the fix, but it now closes one of the more deceptive UI weaknesses in Windows.

0patch’s Alternative, More Defensive Solution

Security company ACROS / 0patch independently developed its own fix, taking a different approach. Instead of showing the entire command, their micropatch blocks suspicious shortcuts altogether:

• If a shortcut contains more than 260 characters in its Target
• and is opened through Windows Explorer
• → Windows truncates it and warns the user

This method disrupts real-world malicious shortcuts identified in campaigns over the past eight years — and protects legacy systems that Microsoft no longer patches.

What Should Windows Users and IT Teams Do This Month?

• 1. Install the December updates — but avoid KB5070311 on production devices

Preview updates are optional and still contain UI-regression bugs.

• 2. Don’t skip the Servicing Stack Update

KB5071142 is required for proper future patching.

• 3. Treat .lnk files with caution

Especially if received via email, messaging apps, or inside ZIP archives.

• 4. Consider endpoint tools that inspect shortcut metadata

Traditional antivirus engines often overlook LNK command fields entirely.

Final Thoughts

December Patch Tuesday 2025 captures the dual nature of modern Windows development:
a push toward slicker interfaces and deeper AI integration, contrasted with an ongoing struggle to maintain transparency and trust in the update process.

On one hand, Windows 11 becomes more refined and more powerful.
On the other, the silent fix of CVE-2025-9491 shows that not all security patches arrive with the clarity or communication users expect.

Corentin C

Founder of ToolsLib, Designer, Web and Cybersecurity Expert.
Passionate about software development and crafting elegant, user-friendly designs.