Some HTML elements, such as <title> and <textarea>, can contain literal angle brackets without treating them as markup. It is possible to pass a literal closing tag to .innerHTML on these elements, and subsequent content after that will be parsed as if it were outside the tag. This can lead to XSS if a site does not filter user input as strictly for these elements as it does for other elements. This vulnerability affects Firefox < 69, Thunderbird < 68.1, Thunderbird < 60.9, Firefox ESR < 60.9, and Firefox ESR < 68.1.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-11744
• https://bugzilla.mozilla.org/show_bug.cgi?id=1562033
• https://security.gentoo.org/glsa/201911-07
• https://usn.ubuntu.com/4150-1
• https://www.mozilla.org/security/advisories/mfsa2019-25
• https://www.mozilla.org/security/advisories/mfsa2019-26
• https://www.mozilla.org/security/advisories/mfsa2019-27
• https://www.mozilla.org/security/advisories/mfsa2019-29
• https://www.mozilla.org/security/advisories/mfsa2019-30
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00009.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00010.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html