Facebook had this bug as far as accepting group requests very early on, maybe around 2010. Early enough that groups were limited to your college.

I wrote a script to accept invitations to every group ID from 1 to 10000. It even added me to groups that didn't exist yet, presumably just adding my ID and the group ID to a table. So when someone created a group to rant about me being in all their groups, I was in it and, as the first member, an admin.

Facebook fixed the bug when I reported it and first kicked me out of my legitimate groups, then fixed that too, though they didn't pay bounties then.