In MyBB before 1.8.11, the Email MyCode component allows XSS, as demonstrated by an onmouseover event.
https://blog.mybb.com/2017/04/04/mybb-1-8-11-merge-system-1-8-11-release/
http://seclists.org/fulldisclosure/2017/Apr/53
Source: Mitre, NVD
Published: 2017-04-24
Updated: 2017-04-27
Base Score: 4.3
Vector: CVSS2#AV:N/AC:M/Au:N/C:N/I:P/A:N
Severity: Medium
Base Score: 6.1
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N