I have been using PortableApps for years and never seen this before. The platform wanted to update to 26.0, but when it started to do so, Avast Antivirus showed a popup saying that it had quarantined PortableApps.com_Platform_Setup_26.0.paf.exe because it was infected with "FileRepMalware [Misc]". Here is a screenshot with the details panel open: https://imgur.com/a/LCyI8Sn
Before I click "Report as false positive", I'd like assurances. I can't remember the last time Avast gave me any false positives - it's not normally twitchy.