CVE-2021-47934Public exploitNetwork attack vector

Script execution and cover changes via unchecked inputs

Published May 16, 2026 · Updated May 16, 2026

Stored XSS and CSRF in MyBB Timeline 1.0 allow remote attackers to execute scripts in profile viewers' browsers and change cover pictures. The plugin renders thread titles, post content, Location, and Bio values as executable profile content, while timeline.php accepts a cover-picture form submission without a request token. Posting or profile-edit access is required to store a script payload, and viewing an affected profile triggers it; the forged cover change requires a logged-in victim to submit the crafted form.

CVSS severity6.9
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS and CSRF in MyBB Timeline 1.0 allow remote attackers to execute scripts in profile viewers' browsers and change cover pictures. The plugin renders thread titles, post content, Location, and Bio values as executable profile content, while timeline.php accepts a cover-picture form submission without a request token. Posting or profile-edit access is required to store a script payload, and viewing an affected profile triggers it; the forged cover change requires a logged-in victim to submit the crafted form.

The record

CVE
CVE-2021-47934
Published
May 16, 2026
Updated
May 16, 2026
Vendor
MyBB
Product
MyBB Timeline
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 16, 2026CVE publishedPublication date reported by the CVE source.
  2. May 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MyBB · MyBB Timelineversion=1.0

Published CVSS scores

5.3VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
6.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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