A buffer overflow in parsing WebP images may result in the execution of arbitrary code.
For Debian 10 buster, this problem has been fixed in version 102.15.1esr-1~deb10u1.
We recommend that you upgrade your firefox-esr packages.
For the detailed security status of firefox-esr please refer to its security tracker page at: https://security-tracker.debian.org/tracker/firefox-esr
Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS