CVE-2023-23603: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.6% chance of exploitation in the next 30 days.

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)

Published 2023-06-02. Last modified 2026-06-17.