Digital Foundry just confirmed what gamers have been screaming about for over a month. The Windows 11 October 2025 update, specifically KB5066835, destroys gaming performance on systems with Nvidia GPUs. Frame rates dropped by 33 to 50 percent in Assassin’s Creed Shadows during testing on a high-end Ryzen 7 9800X3D system paired with an RTX 5090. Microsoft deployed this update automatically to millions of PCs without warning anyone about the performance catastrophe.
The Numbers Don’t Lie
Digital Foundry’s testing methodology was straightforward and damning. They benchmarked Assassin’s Creed Shadows at 4K resolution with maximum graphics settings and DLSS Quality mode enabled. Before applying Nvidia’s emergency hotfix driver, the game struggled to maintain 34 frames per second in certain scenes. After installing the hotfix, those same scenes jumped to 72 FPS. That’s not a small improvement. That’s the difference between unplayable stuttering and smooth gameplay.
The publication shared side-by-side screenshots showing identical moments in the game with wildly different frame rates. One image captured 34 FPS with the broken Windows update installed. The other showed 72 FPS after Nvidia’s fix. The visual evidence confirms that KB5066835 cut performance by more than half in this specific title. Other users testing Counter-Strike 2 reported an 11 percent increase in 1% low frame rates after applying the hotfix, indicating the problem extends beyond just Assassin’s Creed.
What KB5066835 Actually Changed
Microsoft released KB5066835 on October 14, 2025, as part of their regular Patch Tuesday security updates. The update targeted Windows 11 versions 24H2 and 25H2, affecting essentially every modern Windows 11 installation. The official release notes focused on security patches, bug fixes for smart card authentication, and improvements to Windows Cryptographic Services. There was zero mention of potential gaming performance impacts.
Digital Foundry suspects the culprit involves DirectX compliance changes in the update. Microsoft apparently modified something related to how Windows handles graphics rendering without coordinating with GPU manufacturers. Nvidia had to reverse-engineer the problem and develop a workaround driver rather than receiving advance notice about the changes. This lack of communication between Microsoft and hardware partners turned what should have been a routine security patch into a month-long performance disaster for gamers.
Nvidia’s Emergency Response
Nvidia finally acknowledged the problem on November 19, 2025, releasing GeForce Hotfix Display Driver version 581.94. The company’s support document confirmed that lower performance could be observed in some games after updating to Windows 11 October 2025 KB5066835. The wording is deliberately vague, with Nvidia refusing to specify which GPUs or how many games were affected. The driver update appeared on their Customer Care support site rather than going through normal Game Ready Driver channels.
This hotfix driver is technically a beta release that skips Nvidia’s usual quality assurance process. The company pushed it out as quickly as possible to address issues affecting a large number of users. While this approach gets fixes into players’ hands faster, it also means the driver received less extensive testing than normal releases. So far, user reports suggest the hotfix works as advertised without introducing new problems, but your mileage may vary.
How to Fix the Problem Right Now
If you’re experiencing lower frame rates or stuttering in games after mid-October 2025, you have two options. The first and easiest solution is downloading Nvidia’s hotfix driver 581.94. Visit Nvidia’s Customer Care support site or launch GeForce Experience and check for driver updates. The hotfix appears in the update list for compatible GPUs. Download and install it like any other driver update.
For the cleanest installation, perform a full driver uninstall first. Use Display Driver Uninstaller (DDU) to completely remove your current Nvidia drivers, reboot into Safe Mode, then install version 581.94 fresh. This eliminates any potential conflicts from previous driver versions. Make sure your motherboard BIOS and system firmware are also fully updated before installing the new driver.
The second option is uninstalling Windows update KB5066835 entirely. Open Windows Settings, navigate to Windows Update, then click Update History. Scroll to the bottom and select Uninstall Updates. Find KB5066835 in the list and click Uninstall. Windows will warn you that removing updates may put your PC at risk. That’s technically true since KB5066835 contains security patches, but if gaming is your priority, uninstalling restores your previous performance.
After uninstalling KB5066835, restart your computer immediately. Then open Windows Update settings again and disable the option that says “Get the latest updates as soon as they’re available.” This prevents Windows from automatically reinstalling the problematic update. Eventually Microsoft will bundle these security fixes into a future update that hopefully won’t tank gaming performance, but for now this keeps your system stable.
Which Games Are Actually Affected
Here’s where things get frustrating. Nvidia’s documentation only states that “some games” experience lower performance without providing a complete list. The confirmed affected titles based on user testing and Digital Foundry’s investigation include:
- Assassin’s Creed Shadows – Frame rate drops between 33% and 50%
- Counter-Strike 2 – Increased stuttering and lower 1% frame time performance
- Digital Combat Simulator – Significant FPS reduction confirmed by multiple users
Community reports suggest other games might be affected too, but without official confirmation from Nvidia or comprehensive testing, it’s impossible to know the full extent. If you notice any game running worse than usual after mid-October, assume it’s related to KB5066835 and try the fixes. The performance impact varies by title, with some games showing barely noticeable changes while others become nearly unplayable.
Is This Just an Nvidia Problem
The short answer is maybe not. Nvidia is the only GPU manufacturer that publicly acknowledged the issue and released a fix, which strongly suggests the problem primarily affects GeForce graphics cards. However, Windows Latest reports indicate that even AMD and Intel GPU users experienced sluggish performance after KB5066835. Their testing showed possible performance degradation across different hardware configurations.
The lack of statements from AMD or Intel could mean several things. Either their GPUs weren’t affected as severely, the number of impacted users was smaller, or both companies are still investigating. It’s also possible that Microsoft’s DirectX changes affected Nvidia’s driver architecture more significantly due to how GeForce drivers handle certain rendering calls. Until AMD or Intel release official statements, assume this is primarily an Nvidia issue but remain aware that other GPUs might face similar problems.
Performance Comparison Table
| Scenario | FPS Before Fix | FPS After Fix | Improvement |
|---|---|---|---|
| AC Shadows 4K DLSS Quality | 34 FPS | 72 FPS | 112% increase |
| AC Shadows Average Performance | 149.7 FPS | 202.3 FPS | 35% increase |
| Counter-Strike 2 1% Lows | Lower baseline | 11% higher | 11% improvement |
| Test System Specs | AMD Ryzen 7 9800X3D + Nvidia RTX 5090 | ||
Microsoft’s Other October Disasters
The gaming performance catastrophe wasn’t even the only problem with KB5066835. Microsoft also broke Windows Recovery Environment on systems using USB mice and keyboards. Users trying to access WinRE for system recovery found themselves locked out because their input devices stopped working during the recovery process. This meant computers stuck on the recovery screen became essentially unrecoverable without legacy PS/2 peripherals that nobody owns anymore.
After community outrage, Microsoft issued emergency update KB5070773 to patch the WinRE problems. The October update also disabled the preview panel in File Explorer for files downloaded from the internet as part of new security measures. While that change makes sense from a security perspective, Microsoft failed to communicate it properly, leading to confusion about whether File Explorer was broken. The cumulative effect of these issues paints a picture of an update that shipped before proper testing across different hardware configurations and use cases.
Why This Took Over a Month to Fix
KB5066835 deployed on October 14, 2025. Nvidia released their hotfix driver on November 19, 2025. That’s over a month of degraded gaming performance for millions of players. Digital Foundry specifically called out Microsoft for this timeline, noting that if Microsoft knew about DirectX compliance issues with Nvidia drivers, they should have coordinated with Nvidia to release fixes simultaneously with the Windows update.
Instead, Nvidia had to discover the problem through user reports, reproduce the issue in their labs, identify the cause, develop a workaround, and push out an emergency driver update. All of this happened while Microsoft remained silent about the gaming performance impacts. The company’s support documentation for KB5066835 still doesn’t mention gaming issues or recommend installing updated GPU drivers. This lack of transparency and coordination between the world’s largest software company and the dominant GPU manufacturer is frankly embarrassing.
FAQs
What is Windows update KB5066835?
KB5066835 is the October 2025 cumulative security update for Windows 11 versions 24H2 and 25H2. Microsoft released it on October 14, 2025, as part of Patch Tuesday. The update includes security fixes and improvements to Windows Cryptographic Services but also introduced performance problems for gamers.
How do I know if KB5066835 is affecting my gaming performance?
If you notice lower frame rates, increased stuttering, or general performance degradation in games after mid-October 2025, KB5066835 is likely the cause. Check your Windows Update history to see if the update is installed, then compare your current FPS to benchmarks or recordings from before October 14.
Should I install Nvidia driver 581.94?
Only install the 581.94 hotfix driver if you’re experiencing performance issues after the Windows update. If your games are running normally, stick with the latest stable Game Ready Driver. The hotfix is a beta release that skips normal quality assurance testing.
Can I safely uninstall KB5066835?
Yes, but understand that KB5066835 contains security patches. Uninstalling it restores gaming performance but potentially leaves your system vulnerable to security threats. A better solution is keeping the update installed and applying Nvidia’s hotfix driver instead.
Does this problem affect AMD or Intel GPUs?
Nvidia is the only GPU manufacturer that officially confirmed and addressed the issue. Some reports suggest AMD and Intel systems might also experience performance problems, but neither company has released statements or fixes. The problem appears to primarily affect Nvidia GeForce cards.
Which games are confirmed to have performance issues?
Assassin’s Creed Shadows, Counter-Strike 2, and Digital Combat Simulator are confirmed affected. Nvidia stated that “some games” have lower performance but didn’t provide a complete list. Any game experiencing worse performance after October 14 should be considered potentially affected.
Will Microsoft fix this in a future update?
Microsoft has not publicly acknowledged the gaming performance issues or committed to fixing them in future updates. The November 2025 update (KB5068861) did not address the problem, leaving Nvidia’s hotfix driver as the only current solution.
How much performance did KB5066835 actually cost?
Digital Foundry’s testing showed frame rate drops between 33% and 50% in Assassin’s Creed Shadows, with some scenes going from 72 FPS down to 34 FPS. The impact varies by game and hardware configuration, but losses of 30-50% appear common in affected titles.
Conclusion
The KB5066835 disaster reveals serious problems with how Microsoft tests and deploys Windows updates. An automatic security patch that cuts gaming performance in half should never make it to millions of computers without warning labels or advance coordination with GPU manufacturers. The fact that Digital Foundry had to prove the problem existed, that Nvidia took over a month to release a fix, and that Microsoft still hasn’t publicly acknowledged the issue shows complete disregard for the gaming community. This isn’t some obscure edge case affecting three people with weird hardware configurations. This is a mandatory security update deployed to every Windows 11 24H2 and 25H2 system that destroyed frame rates for anyone running Nvidia GPUs in multiple popular games. The solution exists now thanks to Nvidia’s engineers working around Microsoft’s mess, but the damage is done. Players spent money on high-end hardware expecting smooth performance. Instead they got stuttering gameplay and confusion about what went wrong with their systems. Some probably even bought new components thinking their GPUs were failing when the real culprit was sitting in their Windows Update history the whole time. If you’re still running KB5066835 without Nvidia’s hotfix driver, go fix it right now. Download version 581.94, install it clean, and get your frames back. And maybe think twice before letting Windows automatically install the next Patch Tuesday update without checking if it’s going to break something else. Microsoft’s quality control clearly isn’t catching these problems before they ship to consumers.