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CVE-2026-45115

MyBB: Buddy/ignore list username XSS

Published: Aug 18, 2026Updated: Aug 18, 2026 Sources: CVE List NVDCWE-79
8.7HIGH
NVD MITRE
EPSS Score
0.3%
Top 78.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

Description

MyBB is free and open source forum software. Prior to 1.8.40, the Buddy/Ignore component does not sanitize usernames correctly, allowing attackers to perform JavaScript code injection through a specially crafted username. The User CP Buddy/Ignore list and the Select Buddies list in Private Messages pass usernames through htmlspecialchars_uni(), which may leave single quotes unescaped. The payload is triggered when a victim chooses Yes in Please Confirm while removing the username in usercp.php, or selects the username through the onclick handler in the xmlhttp.php Select Buddies popup. The uniquely identifying implementation details include Private Messages Select Buddies list, and unescaped single quotes. This issue is fixed in version 1.8.40.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:CC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-79

Affected Products

mybb
oss-projectaka mybb forums
mybb
Web & CMS Plugins

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Execution
Initial Access
View detailed technique mapping

References

https://github.com/mybb/mybb/releases/tag/mybb_1840
github.com
https://github.com/mybb/mybb/security/advisories/GHSA-p766-qqxv-rfc2
github.com
https://mybb.com/versions/1.8.40
mybb.com

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