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Vulnerability record · CVE-2020-15139 · published 10 August 2020

CVE-2020-15139: Mybb cross-site scripting vulnerability

Mybb · Mybb

In MyBB before version 1.8.24, the custom MyCode (BBCode) for the visual editor doesn't escape input properly when rendering HTML, resulting in a DOM-based XSS vulnerability. The weakness can be exploited by pointing a victim to a page where the visual editor is active (e.g. as a post or Private Message) and operates on a maliciously crafted MyCode message. This may occur on pages where message content is pre-filled using a GET/POST parameter, or on reply pages where a previously saved malicious message is quoted. After upgrading MyBB to 1.8.24, make sure to update the version attribute in the `codebuttons` template for non-default themes to serve the latest version of the patched `jscripts/bbcodes_sceditor.js` file.

6.1 CVSS 3.1 Medium EPSS 1.3% · top 29.7% CWE-79 · Cross-site scripting
6.1CVSS 3.1 base score, v2 4.3
1.3%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

Description

In MyBB before version 1.8.24, the custom MyCode (BBCode) for the visual editor doesn't escape input properly when rendering HTML, resulting in a DOM-based XSS vulnerability. The weakness can be exploited by pointing a victim to a page where the visual editor is active (e.g. as a post or Private Message) and operates on a maliciously crafted MyCode message. This may occur on pages where message content is pre-filled using a GET/POST parameter, or on reply pages where a previously saved malicious message is quoted. After upgrading MyBB to 1.8.24, make sure to update the version attribute in the `codebuttons` template for non-default themes to serve the latest version of the patched `jscripts/bbcodes_sceditor.js` file.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/mybb/mybb/commit/37ad29dcd25489a37bdd89ebac761f22492558b0 PatchThird Party Advisory
https://github.com/mybb/mybb/security/advisories/GHSA-37h7-vfv6-f8rj PatchThird Party Advisory
https://mybb.com/versions/1.8.24/ PatchVendor Advisory
https://github.com/mybb/mybb/commit/37ad29dcd25489a37bdd89ebac761f22492558b0 PatchThird Party Advisory
https://github.com/mybb/mybb/security/advisories/GHSA-37h7-vfv6-f8rj PatchThird Party Advisory
https://mybb.com/versions/1.8.24/ PatchVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2020-15139), CISA KEV, FIRST EPSS (scores of 2026-10-16). This page is refreshed as NVD updates the record.