The remote Debian host is missing a security-related update.
Multiple security issues have been found in the Mozilla Firefox web browser, which could potentially result in the execution of arbitrary code, cross-site scripting, bypass of the same-origin policy, sandbox escape, information disclosure or denial of service.
Upgrade the firefox-esr packages. For the oldstable distribution (stretch), these problems have been fixed in version 60.9.0esr-1~deb9u1. For the stable distribution (buster), these problems have been fixed in version 60.9.0esr-1~deb10u1.