Gertjan

**Name of the Vulnerable Software and Affected Versions** Firefox ESR versions prior to 91.11 Thunderbird versions prior to 102 Thunderbird versions prior to 91.11 Firefox versions prior to 101 **Description** An attacker could have injected CSS into stylesheets accessible via internal URIs, such as `resource:`, and in doing so bypass a page's Content Security Policy. This issue is related to an error in processing CSS stylesheets accessible through internal URIs. Exploitation of this issue may allow a remote attacker to bypass the implemented Content Security Policy. **Recommendations** For Firefox ESR versions prior to 91.11, update to version 91.11 or later. For Thunderbird versions prior to 102, update to version 102 or later. For Thunderbird versions prior to 91.11, update to version 91.11 or later. For Firefox versions prior to 101, update to version 101 or later. As a temporary workaround, consider disabling access to internal URIs, such as `resource:`, until a patch is available.