If you have some specific data applicable to this exact problem, I'd love to hear that specific relevant data. In the beta, we (my team) had a bug wherein ACLs were incorrectly migrated in one particular scenario, causing a very similar lack of functionality.
An educated guess as to this problem would indicate that ACLs are probably being reset by the upgrade path. But without a machine to look at in person, I can only hand wave over the problem. Clearly the machine should not hit this problem and if it does
hit this problem it should recover as cleanly as possible. Both parts of that statement are not being met right now, and I apologize for that. This is a bug, and I need more data in person to work upon it. Malware is not involved here.
There are many thousands or millions or hours of testing involved previous to release. It does not and can not catch everything: that's part of the reality of computing. This is a legitimate technical issue probably caused by one particular code path.
Please please do not distract or confuse users by bringing up non-germane data. If you have specific data that correlates to this problem, I'm all ears. But until you have specific data, I, as someone who has personally actively fought against malware and
helped shut down botnets, would ask you to stay relevant to the topic at hand which is solely ACL corruption on a folder that malware does not have access to.