What’s Vulnerable › Vulnerabilities

CVE-2023-23603: Calls to console.log allowed bypassing Content Security Policy via format directive

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-06-02 · updated 2026-06-17
• Weakness: CWE-770

Description

Regular expressions used to filter out forbidden properties and values from style directives in calls to `console.log` weren't accounting for external URLs. Data could then be potentially exfiltrated from the browser. This vulnerability affects Firefox < 109, Firefox ESR < 102.7, and Thunderbird < 102.7.

Affected products

• Mozilla Firefox: before 109.0 — fixed in 109.0
• Mozilla Firefox ESR: before 102.7 — fixed in 102.7
• Mozilla Thunderbird: before 102.7 — fixed in 102.7

How to fix

Upgrade to a fixed version: Mozilla Firefox 109.0; Mozilla Firefox ESR 102.7; Mozilla Thunderbird 102.7. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1800832
• https://www.mozilla.org/security/advisories/mfsa2023-01/
• https://www.mozilla.org/security/advisories/mfsa2023-02/
• https://www.mozilla.org/security/advisories/mfsa2023-03/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1800832
• https://www.mozilla.org/security/advisories/mfsa2023-01/
• https://www.mozilla.org/security/advisories/mfsa2023-02/
• https://www.mozilla.org/security/advisories/mfsa2023-03/

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