The Mozilla Maintenance Service "helper.exe" application creates a temporary directory writable by non-privileged users. When this is combined with creation of a junction (a form of symbolic link), protected files in the target directory of the junction can be deleted by the Mozilla Maintenance Service, which has privileged access. Note: This attack requires local system access and only affects Windows. Other operating systems are not affected. This vulnerability affects Firefox ESR < 52.2 and Firefox < 54.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-7761
• https://bugzilla.mozilla.org/show_bug.cgi?id=1215648
• https://sourceforge.net/p/nsis/bugs/1125/
• https://www.mozilla.org/security/advisories/mfsa2017-15/
• https://www.mozilla.org/security/advisories/mfsa2017-16/
• http://www.securityfocus.com/bid/99057
• http://www.securitytracker.com/id/1038689