I have a document library that has unique permissions. A SP group has only rights to view documents in the library. All documents inside the library inherit the access rights from the library (so no unique permissions there).
Now there is a strange behaviour. The library contains pictures (jpeg, png) and also files like pdf etc.. Providing a user with a link from a jpg in the library he is able to open that jpg. Providing the same user with a link to one of the pdfs in the library he gets an permission error (this site has not been shared with you). So all pictures can be viewed but no documents. Strange...
I have to add that the view right is very limited. The users cannot go to the teamsite and browse the library directly. They can only access the files if they know the direkt link. This has worked for a long time and still works on a copy of the affected Teamsite with exact same permissions set.
I wonder if anyone ever had a problem like that and can help.