Islandora does not sufficiently check file update access when processing media source and derivative uploads

Islandora does not sufficiently check file update access when processing media source and derivative uploads. A user with permission to update media or create derivatives can submit a crafted request to overwrite files they are not authorized to modify, including private files.

The Islandora Text Extraction submodule also bypasses shared destination URI and file extension validation when attaching OCR output.

This vulnerability is mitigated by the fact that an attacker must have permission to update media or to update a node and create media.