I suspect this is a result of bug 80289. I just ran a mass change on my local bugzilla install and noticed that any bug in a group had its groupset reset to '0'.

the change multiple bugs form calls process_bug.cgi, which now assumes if it doesn't find anything mentioning groups that everything is being cleared, since empty checkboxes aren't transmitted. When we were using select boxes for the groups, the absense of a select box altogether resulted in no action. The easiest way to fix this is probably going to be to create some sort of "--do_not_change--" value for groups on the mass change page... If we have to go this far, maybe we should go ahead and implement being able to change groups from the mass change page... (isn't there a bug for that already somewhere?)

yep, there was a bug for that already. It's now a dependency on this one.

adding patch keyword to get this out of the "needs code" queue, since there's a patch that covers this on bug 84714.

Bug 84714 contained a patch which fixed this, and it was just checked in.

Moving to Bugzilla product