CVE-2021-30157Public exploitNetwork attack vector

Stored XSS via unescaped filter-label append

Published Apr 6, 2021 · Updated Aug 3, 2024

Cross-site scripting in MediaWiki before 1.31.12 and 1.32.0 through 1.35.1 allows remote authenticated users to execute script in visitors' browsers. The TagItemWidget update path passes an editable rcfilters-filter-*-label message to jQuery append(), interpreting its contents as HTML instead of text. Exploitation requires an administrator to modify a system message and a visitor to load or select the affected filter on RecentChanges or Watchlist.

CVSS severity6.1
Medium
EPSS probability1.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in MediaWiki before 1.31.12 and 1.32.0 through 1.35.1 allows remote authenticated users to execute script in visitors' browsers. The TagItemWidget update path passes an editable rcfilters-filter-*-label message to jQuery append(), interpreting its contents as HTML instead of text. Exploitation requires an administrator to modify a system message and a visitor to load or select the affected filter on RecentChanges or Watchlist.

The record

CVE
CVE-2021-30157
Published
Apr 6, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Apr 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
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/JScript

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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