CVE-2019-17020

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-01-08 · updated 2026-06-17
Weakness: CWE-611

Description

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.

Affected products

Canonical Ubuntu Linux: 16.04, 18.04, 19.04, 19.10
Mozilla Firefox: before 72.0 — fixed in 72.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 72.0. Check the vendor advisory for mitigations.

References

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

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