firefox regressions

USN-5186-1 fixed vulnerabilities in Firefox. The update introduced several
minor regressions. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

Multiple security issues were discovered in Firefox. If a user were
tricked into opening a specially crafted website, an attacker could
potentially exploit these to cause a denial of service, obtain sensitive
information, conduct spoofing attacks, bypass CSP restrictions, or
execute arbitrary code. (CVE-2021-43536, CVE-2021-43537, CVE-2021-43538,
CVE-2021-43539, CVE-2021-43541, CVE-2021-43542, CVE-2021-43543,
CVE-2021-43545, CVE-2021-43546)

A security issue was discovered with the handling of WebExtension
permissions. If a user were tricked into installing a specially crafted
extension, an attacker could potentially exploit this to create and
install a service worker that wouldn't be uninstalled with the extension.
(CVE-2021-43540)