CVE-2025-5266
MediumCVSS 4.3Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.
Risk Assessment
An attacker can exploit the information leak to infer the state of cross-origin resources, potentially leading to user privacy violations. The risk affects browser and email client users prior to updating.
Recommendation
Update Firefox to version 139 (or ESR 128.11) and Thunderbird to version 139 (or 128.11). Enforce automatic updates across the organization.
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Original NVD description (English source)
Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS