calibre is an e-book manager. Prior to 9.12.0, the calibre Content Server endpoint POST /book-update-annotations/{library_id}/{book_id}/{fmt} in src/calibre/srv/books.py omits needs_db_write=True, causing Router.dispatch() to skip ctx.check_for_write_access() before update_annotations() passes attacker-controlled JSON to db.merge_annotations_for_book(), which allows a readonly user or an anonymous user on an unauthenticated deployment to persist unauthorized book annotation changes. This issue is fixed in version 9.12.0.
https://github.com/kovidgoyal/calibre/security/advisories/GHSA-5x64-w63v-x2g6
https://github.com/kovidgoyal/calibre/releases/tag/v9.12.0
https://github.com/kovidgoyal/calibre/commit/71295e8b62801e1ccecaa4fac47e6942f11cfe1e