The problem occurs when virtualssuser is created for pre-emptive screenshot generation to run its logic when saving content items. However, it is not logged out in some specific scenarios.
The problem might lead to background jobs being executed in the context of virtualssuser. As a result, Audit messages that indicate item modifications may appear in the log files for this user. Also, if the license has a limited number of concurrent editors, the issue might lead to frequently reaching the limit.
To fix the issue, download and apply the patch (follow the instructions in the readme file): Sitecore.Support.154580.
The patch addresses the issue that the virtualssuser is incorrectly logged out, which can be checked at the following page: [hostname]/sitecore/client/Applications/LicenseOptions/KickUser.aspx
After applying the patch there should not be virtualssuser entries (which means that Sitecore XP instance does not have active sessions for this virtual user), and the background tasks should then not be performed in the context of this user.
Disable the Sitecore.ContentTesting.PreemptiveScreenshot.config file to disable automatic screenshot generation.
The pre-emptive screenshot generation event handlers generate screenshot files as items change, which reduces waiting time within the UI when screenshots are displayed. The downside is a longer waiting time before the screenshot becomes available when creating a test or checking test reports.