It's not just Mailman. I first saw the crash on bugs.busybox.net. I log into the site just fine, but when I click on the link to view my account info, FF crashes every time. BusyBox bug tracking is run by Mantis if that helps anyone.
I think the difference between mailman and some others like launchpad and busybox is the latter store a cookie locally to allow you to get back in across restarts of FF without having to retype your password. Mailman is much simpler and just asks for your password every time (maybe the cookie is per-session instead of being saved). This, of course, is a complete guess on my part. It also doesn't explain very well why clicking the "My Account" link in busybox causes the problem. There are lots and lots of dups of this issue. I posted another recipe to reproduce in bug #77998 -- Firefox: saved passwords causes crash with Mailman admin page https://launchpad.net/bugs/77859 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs