October update for Windows 11 reduces frame rates by up to 50%

Microsoft has released a recent security and functionality update for Windows 11 (KB5066835) that has been shown to impact game performance, with frame rate drops of up to 50%. The issue, which has persisted since the October patch release, has been confirmed by conclusive tests from Digital Foundry.

The technology site tested the problem by running benchmarks on Assassin's Creed Shadows, using an AMD Ryzen 9800X3D and an Nvidia RTX 5090. After observing "notably low" frame rates, Digital Foundry installed a recent hotfix driver from Nvidia, which specifically addresses the "Lower Performance [...] in some games after updating to Windows 11 October 2025 KB5066835". With the installed adjustment, frame rates jumped.

Although the site did not provide the exact change in average frame rate, the screenshots presented showed the same point in the game with frame rates of 34fps and 72fps before and after the hotfix, respectively. They indicated that the recent Windows update, if not fixed, reduced performance in Assassin's Creed Shadows by between 33 and 50%.

While Digital Foundry's test focused on just one game, other reports suggest a broader issue. A user on X (formerly Twitter) tested the hotfix on CS2 and reported an 11% increase in the 1% lows (lower frame rates) with the patch applied. Nvidia's own documentation states that the hotfix corrects "some games", suggesting that several other titles may be affected.

Uncertainty persists as to whether the issue is exclusive to Nvidia GPUs or if it affects AMD graphics cards. Further testing will be required to fully clarify the extent of the flaw. Players using a recent Nvidia GPU who have noticed a drop in gameplay performance after the update should download the Nvidia hotfix.