If the "app.support.baseURL" preference is changed by a malicious local program to contain HTML and script content, this content is not sanitized. It will be executed if a user loads "chrome://browser/content/preferences/in-content/preferences.xul" directly in a tab and executes a search. This stored preference is also executed whenever an EME video player plugin displays a CDM-disabled message as a notification message. This vulnerability affects Firefox < 59.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-5133
• https://bugzilla.mozilla.org/show_bug.cgi?id=1430511
• https://bugzilla.mozilla.org/show_bug.cgi?id=1430974
• https://usn.ubuntu.com/3596-1/
• https://www.mozilla.org/security/advisories/mfsa2018-06/
• http://www.securityfocus.com/bid/103386
• http://www.securitytracker.com/id/1040514