{"id":"CVE-2021-39338","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-39338","generatedAt":"2026-10-27T17:39:09.400Z","title":"The MyBB Cross-Poster WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and sanitization via several parameters found in the ~/classes/MyBBXPSettings.php file which allowed attackers with administrative…","description":"The MyBB Cross-Poster WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and sanitization via several parameters found in the ~/classes/MyBBXPSettings.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 1.0. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.","published":"2021-10-15T13:15:08.000Z","lastModified":"2026-06-17T04:03:35.000Z","status":"Modified","sourceIdentifier":"security@wordfence.com","cvss":{"version":"3.1","score":4.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N"},"cwe":["CWE-79"],"affected":["mybb cross-poster project/mybb cross-poster"],"epss":{"score":0.00946,"percentile":0.60881,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.95%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://github.com/BigTiger2020/word-press/blob/main/MyBB%20Cross-Poster.md","tags":["Exploit","Third Party Advisory"],"source":"security@wordfence.com"},{"url":"https://plugins.trac.wordpress.org/browser/mybb-cross-poster/trunk/classes/MyBBXPSettings.php","tags":["Patch","Third Party Advisory"],"source":"security@wordfence.com"},{"url":"https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39338","tags":["Third Party Advisory"],"source":"security@wordfence.com"},{"url":"https://github.com/BigTiger2020/word-press/blob/main/MyBB%20Cross-Poster.md","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://plugins.trac.wordpress.org/browser/mybb-cross-poster/trunk/classes/MyBBXPSettings.php","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39338","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-39338","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}