For native-to-JS bridging the app requires a unique token to be passed that ensures non-app code can't call the bridging functions. That token could leak when used for downloading files. This vulnerability affects Firefox for iOS < 26.
https://www.mozilla.org/security/advisories/mfsa2020-19/
https://bugzilla.mozilla.org/show_bug.cgi?id=1631739
Source: Mitre, NVD
Published: 2020-07-09
Updated: 2021-07-21
Base Score: 4.3
Vector: CVSS2#AV:N/AC:M/Au:N/C:P/I:N/A:N
Severity: Medium
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N