TikiWiki 1.8.0 to 1.8.2 had a permission bug that was fixed for 1.8.3. I'd advise admins of such Tikis to check if they need a patch/upgrade or not just by reading the following.
When an object is deleted, all objects of the same type lose custom permissions.
By example, if a user deletes an image gallery, all other image galleries get back to default permissions. This will be most dangerous if a user is admin (or have the right to remove) of any Wiki page. If other Wiki pages on this Tiki have higher access restrictions than the default one, the user can get access to those pages by deleting the page he has the right to remove.
Revision 1.373.2.43 of tikilib.php fixes that bug with following diff : http://cvs.sourceforge.net/viewcvs.py/tikiwiki/tiki/lib/tikilib.php?r1=1.373.2.42&r2=1.373.2.43