{"id":"CVE-2025-46734","summary":"league/commonmark Cross-site Scripting vulnerability in Attributes extension","details":"league/commonmark is a PHP Markdown parser. A cross-site scripting (XSS) vulnerability in the Attributes extension of the league/commonmark library (versions 1.5.0 through 2.6.x) allows remote attackers to insert malicious JavaScript calls into HTML. The league/commonmark library provides configuration options such as `html_input: 'strip'` and `allow_unsafe_links: false` to mitigate cross-site scripting (XSS) attacks by stripping raw HTML and disallowing unsafe links. However, when the Attributes Extension is enabled, it introduces a way for users to inject arbitrary HTML attributes into elements via Markdown syntax using curly braces. Version 2.7.0 contains three changes to prevent this XSS attack vector: All attributes starting with `on` are considered unsafe and blocked by default; support for an explicit allowlist of allowed HTML attributes; and manually-added `href` and `src` attributes now respect the existing `allow_unsafe_links` configuration option. If upgrading is not feasible, please consider disabling the `AttributesExtension` for untrusted users and/or filtering the rendered HTML through a library like HTMLPurifier.","aliases":["GHSA-3527-qv2q-pfvx"],"modified":"2026-04-21T03:47:58.565379Z","published":"2025-05-05T19:52:59.521Z","database_specific":{"cwe_ids":["CWE-79"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/46xxx/CVE-2025-46734.json","cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/46xxx/CVE-2025-46734.json"},{"type":"ADVISORY","url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-3527-qv2q-pfvx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-46734"},{"type":"FIX","url":"https://github.com/thephpleague/commonmark/commit/f0d626cf05ad3e99e6db26ebcb9091b6cd1cd89b"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/thephpleague/commonmark","events":[{"introduced":"fc33ca12575e98e57cdce7d5f38b2ca5335714b3"},{"fixed":"6fbb36d44824ed4091adbcf4c7d4a3923cdb3405"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-46734.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"}]}