Activity Stream can display content from sent from the Snippet Service website. This content is written to innerHTML on the Activity Stream page without sanitization, allowing for a potential access to other information available to the Activity Stream, such as browsing history, if the Snipper Service were compromised. This vulnerability affects Firefox < 68.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-11718
• https://bugzilla.mozilla.org/show_bug.cgi?id=1408349
• https://security.gentoo.org/glsa/201908-12
• https://www.mozilla.org/security/advisories/mfsa2019-21/
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html