Dear all, we have on Windows Server 2016 Standard Server running as Terminal Server on our ESX 6.7 Cluster. VM Info: Hostname: TS02 Systemname: Microsoft Windows Server 2016 Standard Systemversion: 10.0.14393 Build 14393 OS Vendor: Microsoft Corporation Hardware Vendor: VMware, Inc. Modell: VMware Virtual Platform Systemtyp: x64-based PC Hotfix(es): [01]: KB3186568, [02]: KB3192137, [03]: KB4013418, [04]: KB4023834, [05]: KB4035631, [06]: KB4049065, [07]: KB4089510, [08]: KB4091664, [09]: KB4093137, [10]: KB4132216, [11]: KB4465659, [12]: KB4467694, [13]: KB4471331, [14]: KB4477029, [15]: KB4467691 Firefox Version: 63.0.3 (Also tested LTS 60.0.3) Kaspersky: Security for Win Srv 10.1.1.746 Windows Defender is Disabled Unfortunately, since about 4 Month our Firefox installation is causing a crash of the user experience service. We have no Windows logs regarding this problem at all, the only thing we see is that the service is being forcefully terminated at shutdown. The problem/crash shows up in the following chronology: - A user is opening a "filename.html" file out of an outlook e-mail attachment in Firefox. Firefox is the default browser on the system. - The firefox crashes on the user session and the user is not able to start Firefox again. - About 5 Minutes after the first crash, other users are complaining about poor performance in their remote session. Beside the performance problem other firefox Windows from other users start to freeze. Users that logout from their session can only see a black screen after the login prompt when they try to login again. Admins can only login through the vmware console to the server, since their sessions are black too. - About 10 Minutes after the first crash the whole system is extremely slowly and no one can use firefox anymore since all Firefox Windows in all sessions are frozen. - About 15 Minutes after the first crash the system has to be rebooted because it is not usable anymore. After the server is rebooted, everything works fine. Even files from outlook attachments can be opened fine. After about 24 hours to 5 days everything begins from start again. We already have tried LTS versions of Firefox with no luck. Windows Updates are installed, Kaspersky for Server is on the latest patch release. At the moment we have configured a GPO object that prevents the firefox.exe from being executed and the problem is not showing up again. But since our internal CRM Software is only Firefox and (partly) IE compatible, we urgently need Firefox back as soon as possible. I've found some crash reports from Firefox, gut did not get any (for me/us) usable information out of it. Any help would be greatly appreciated. Kind regards, Val