Reports indicate performance can drop by as much as 50% in certain scenarios.
A recent Windows 11 update, KB5066835 (October 2025), has produced significant performance regressions in games — most noticeably in Ubisoft’s Assassin’s Creed Shadows.
Digital Foundry’s tests corroborate this: with KB5066835 applied and no hotfix installed, a system equipped with a Ryzen 7 9800X3D and an RTX 5090 experienced FPS declines of roughly 33–50% during demanding scenes.
Earlier this week NVIDIA issued the GeForce Hotfix Driver 581.94 to address the problem.
Reporters have reached out to Microsoft for clarification but have not yet received a reply.
In other AC Shadows updates: the game recently added an Attack on Titan crossover and was updated to patch 1.1.6.
Source: iXBT.games