Command line arguments could have been injected during Firefox invocation as a shell handler for certain unsupported file types. This required Firefox to be configured as the default handler for a given file type and for a file downloaded to be opened in a third party application that insufficiently sanitized URL data. In that situation, clicking a link in the third party application could have been used to retrieve and execute files whose location was supplied through command line arguments. Note: This issue only affects Windows operating systems and when Firefox is configured as the default handler for non-default filetypes. Other operating systems are unaffected. This vulnerability affects Firefox < 73 and Firefox < ESR68.5.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-6799
• https://bugzilla.mozilla.org/show_bug.cgi?id=1606596
• https://security.gentoo.org/glsa/202003-02
• https://www.mozilla.org/security/advisories/mfsa2020-05/
• https://www.mozilla.org/security/advisories/mfsa2020-06/