This advisory is to formally inform you of a recently identified issue affecting Virtual Desktop launches and connections when using the Omnissa Horizon Windows Client. The issue arises after the installation of the Microsoft Windows Patch update KB5066835 on end-user devices. Recommended Mitigation Strategy To ensure service continuity while a permanent resolution is being developed, please take the following actions based on your current environment: 1. If KB5066835 has not yet been installed: 2. Action: We strongly recommend deferring the installation of the Recent Windows update (KB5066835) until an official corrective patch from Omnissa or Microsoft is released and validated. 3. If KB5066835 has already been installed and desktop connection issues are observed: a. Option A (Client-Based Mitigation): Temporarily uninstall updates KB5066835 and its prerequisite KB5065789 from affected devices. b. Option B (Interim Access): Use the Horizon HTML Client (browser-based access) as a fully functional workaround to maintain connectivity to your virtual desktop. Status and Resolution The Horizon Engineering Team has assigned the highest priority to this issue. We are actively investigating the root cause and collaborating closely with relevant partners to identify, test, and release a validated fix at the earliest possible time. We will issue a follow-up communication as soon as a corrective update becomes available or if there are any significant developments in the resolution process. We sincerely appreciate your patience, cooperation, and understanding as we work diligently to restore full functionality and stability. If you have any questions regarding the prerequisites or this update, please contact Omnissa Support. Sincerely, The Horizon Cloud Service Team

it also seems to break all sorts of stuff that use loopback, http/2, etc

I did hear people complaining about IIS related apps like Visual Studio...must be related.

i also saw aws' saml vpn auth, AD on server 2025, seems like a real winner of a patch tuesday

Microsoft has caused a bit of havoc with this latest Sept round of patches

i did see a second mail go out late yesterday that apparently microsoft "fixed" the problem, though it doesn't necessarily make sense what they did to do so... something to look for this morning i guess, since i didnt see any new patches download to my machine

cool, thanks Rob

I was thinking the same thing Rob! Like, what about those that already installed the October update! I believe it was only on the Horizon Cloud Service v2 service, so maybe it was patched on the backend.

oh no it was definitely more than just horizon - it affected the httplistener that's part of the IIS or .net code apparently. I've seen a number of programs mentioned, including a lot of custom ones - and apparently they pushed something through defender to fix it (uh, ok..)