CVE-2019-17020 — If an XML file is served with a Content Security Policy and the XML file include

If an XML file is served with a Content Security Policy and the XML file includes an XSL stylesheet, the Content Security Policy will not be applied to the contents of the XSL stylesheet. If the XSL sheet e.g. includes JavaScript, it would bypass any of the restrictions of the Co

01What is this vulnerability?

If an XML file is served with a Content Security Policy and the XML file includes an XSL stylesheet, the Content Security Policy will not be applied to the contents of the XSL stylesheet. If the XSL sheet e.g. includes JavaScript, it would bypass any of the restrictions of the Content Security Policy applied to the XML document. This vulnerability affects Firefox < 72.

02Affected products

Vendor	Product	Versions
Mozilla	Firefox	before 72

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-01-08T21:29:16.000Z
• Last modified: 2024-08-05T01:24:48.668Z

09References

• bugzilla.mozilla.org — https://bugzilla.mozilla.org/show_bug.cgi?id=1597645
• www.mozilla.org — https://www.mozilla.org/security/advisories/mfsa2020-01/
• usn.ubuntu.com — https://usn.ubuntu.com/4234-1/