{"id":"CVE-2021-39338","aliases":["EUVD-2021-25699","GHSA-p7r5-mv7j-8m3r"],"status":"published","title":"MyBB Cross-Poster \u003c= 1.0 Authenticated Stored Cross-Site Scripting","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.","severity":{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00946,"percentile":0.61384,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-79"],"published":"2021-10-15T12:15:41Z","modified":"2026-06-17T04:03:34Z","products":[{"vendor":"mybb cross-poster","product":"mybb cross-poster"},{"vendor":"mybb_cross-poster_project","product":"mybb_cross-poster"}],"references":[{"url":"https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39338","tags":["x_refsource_MISC","x_transferred","Third Party Advisory"]},{"url":"https://github.com/BigTiger2020/word-press/blob/main/MyBB%20Cross-Poster.md","tags":["x_refsource_MISC","x_transferred","Exploit","Third Party Advisory"]},{"url":"https://plugins.trac.wordpress.org/browser/mybb-cross-poster/trunk/classes/MyBBXPSettings.php","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-39338"},{"url":"https://github.com/advisories/GHSA-p7r5-mv7j-8m3r"}],"sources":{"cve":[{"id":"CVE-2021-39338","title":"MyBB Cross-Poster \u003c= 1.0 Authenticated Stored Cross-Site Scripting","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.","status":"published","published":"2021-10-15T12:15:41.796Z","modified":"2025-03-31T17:59:47.215Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:33:09.540052Z"}],"euvd":[{"id":"EUVD-2021-25699","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.","status":"published","published":"2021-10-15T12:15:41Z","modified":"2025-03-31T17:59:47Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T20:52:46.759966Z"}],"ghsa":[{"id":"GHSA-p7r5-mv7j-8m3r","title":"The MyBB Cross-Poster WordPress plugin is vulnerable to Stored Cross-Site Scripting due to...","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.","status":"published","published":"2022-05-24T19:17:44Z","modified":"2023-01-30T05:02:52Z","cwes":["CWE-79"],"updated_at":"2026-11-02T14:46:43.616467Z"}],"nvd":[{"id":"CVE-2021-39338","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.","status":"published","published":"2021-10-15T13:15:07.893Z","modified":"2026-06-17T04:03:34.5Z","cvss":[{"version":"3.1","score":5.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary"},{"version":"2.0","score":2.1,"vector":"AV:N/AC:H/Au:S/C:N/I:P/A:N","level":"low","assessor":"primary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:06:59.689345Z"}]}}