{"cve":"CVE-2021-27889","nvd":{"published":"2021-03-15T17:15:22.517","modified":"2026-06-17T03:45:33.900","status":"Modified","description":"Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","score":6.1},"cwes":["CWE-79"],"references":["http://packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.html","https://blog.sonarsource.com/mybb-remote-code-execution-chain","https://github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcm","http://packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.html","https://blog.sonarsource.com/mybb-remote-code-execution-chain"],"products":["mybb:mybb"],"source":"nvd","synced_at":"2026-10-19T21:15:50.279857260+00:00"},"epss":{"cve":"CVE-2021-27889","score":0.05072,"percentile":0.92331,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}