Exposure of Resource to Wrong Sphere Affecting firefox package, versions <87.0-1

Note: Versions mentioned in the description apply only to the upstream firefox package and not the firefox package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

If an attacker is able to alter specific about:config values (for example malware running on the user's computer), the Devtools remote debugging feature could have been enabled in a way that was unnoticable to the user. This would have allowed a remote attacker (able to make a direct network connection to the victim) to monitor the user's browsing activity and (plaintext) network traffic. This was addressed by providing a visual cue when Devtools has an open network socket. This vulnerability affects Firefox < 87.

• https://security-tracker.debian.org/tracker/CVE-2021-23985
• https://security.gentoo.org/glsa/202104-10
• https://bugzilla.mozilla.org/show_bug.cgi?id=1659129
• https://www.mozilla.org/security/advisories/mfsa2021-10/