Firefox used to cache the last filename used for printing a file. When generating a filename for printing, Firefox usually suggests the web page title. The caching and suggestion techniques combined may have lead to the title of a website visited during private browsing mode being stored on disk. This vulnerability affects Firefox < 89.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-29960
• https://bugzilla.mozilla.org/show_bug.cgi?id=1675965
• https://security.gentoo.org/glsa/202107-09
• https://www.mozilla.org/security/advisories/mfsa2021-23/