Provide references for CVE-2021-27889.
Where can I find more information about CVE-2021-27889?
References are available at: 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.