If a Content Security Policy (CSP) directive is defined that uses a hash-based source that takes the empty string as input, execution of any javascript: URIs will be allowed. This could allow for malicious JavaScript content to be run, bypassing CSP permissions. This vulnerability affects Firefox < 69 and Firefox ESR < 68.1.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-11738
• https://bugzilla.mozilla.org/show_bug.cgi?id=1452037
• https://www.mozilla.org/security/advisories/mfsa2019-25/
• https://www.mozilla.org/security/advisories/mfsa2019-26/
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html