Given an installed malicious file picker application, an attacker was able to steal and upload local files of their choosing, regardless of the actually files picked. *Note: This issue only affected Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox ESR < 68.11.
https://www.mozilla.org/security/advisories/mfsa2020-31/
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1475835%2C1652364