spinoff of Bug 393945, Bug 345572, and Bug 394299. See screenshot for example.

dupe ? https://bugzilla.mozilla.org/show_bug.cgi?id=345808 maybe there are some similar bugs.

No, this is for the underlying issue and that bug is specifically for the Security prefpane which I believe is fixed now by the checkin of Bug 393945.

Though Bug 393945 may not have fixed the security pref pane per Bug 393945 comment #10

To get this 'cutoff' completely fixed, replace in preferences.css: .bottomBox{padding-bottom:2px} with: prefpane>.content-box{padding-bottom:4px} as not not all panes have a 'bottomBox', but all do have a '.content-box'. This ensures that all panes will not be cut off (or at least give it less chance to do so). (see bug 394299)

I highly suspect that this would just lessen the likelihood of this happening and it does not fix the actual underlying issue which this bug is about.

The hack added in bug 283697 and its dependencies can be removed once this is fixed