Not quite sure where to post this one.
The updater in beta5 just suggested that I update my XAMPP launcher to v1.4, but the XAMPP page at https://portableapps.com/apps/development/xampp still lists v1.3 as being current.
1.4 is indeed available on SF, and the updater installs it fine, so I'm guessing that the web page is off. (I did a quick search, and couldn't see any release announcement for 1.4 anywhere either).