Multiple security issues have been found in the Mozilla Firefox web
browser, which could potentially result in the execution of arbitrary code, information disclosure, denial of service or spoofing.
For the oldstable distribution (buster), these problems have been fixed
in version 91.5.0esr-1~deb10u1. Not all architectures are available for oldstable yet, most notably i386 (32 bits x86) is missing.
For the stable distribution (bullseye), these problems have been fixed in version 91.5.0esr-1~deb11u1.
We recommend that you upgrade your firefox-esr packages.