Can't seem to find anything specific to my situation using search, if the information I need is out there, it's been buried due to common words such as "groups" and "user". Official VB site, this one and google haven't helped me, trying to get to the bottom of this for 3 days now.
edit:
Managed to find one other thread about this, but it didn't help. It talks about mods being installed causing it, but my situation is on a clean install. All that shows up in plugins or products is CMS and Blog stuff that came with it.
https://vborg.vbsupport.ru/showthread.php?t=234928
Edit #2:
Disabling the blog from product manager seems to solve this. VB is blaming it on something called suhosin, but not everyone seems to even have suhosin on their servers, plus some of us are on shared hosting and can do nothing about it.
Disable blog -> work on user groups -> enable blog, seems to be the only reasonable solution for now.