CVE-2021-30458Public exploitNetwork attack vector

Cross-site scripting via spoofed internal foster comments

Published Apr 9, 2021 · Updated Aug 3, 2024

Cross-site scripting in Wikimedia Parsoid before 0.11.1 and 0.12.0 through 0.12.1 allows remote attackers to inject meta elements. During tree building, WTUtils::reinsertFosterableContent treats input JSON comments bearing an internal @type property as fostered Parsoid content and reconstructs their attributes after sanitization. A victim must view the generated HTML; the demonstrated injection is limited to body-level meta elements, and no executable script payload is publicly documented.

CVSS severity6.1
Medium
EPSS probability0.98%
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 Wikimedia Parsoid before 0.11.1 and 0.12.0 through 0.12.1 allows remote attackers to inject meta elements. During tree building, WTUtils::reinsertFosterableContent treats input JSON comments bearing an internal @type property as fostered Parsoid content and reconstructs their attributes after sanitization. A victim must view the generated HTML; the demonstrated injection is limited to body-level meta elements, and no executable script payload is publicly documented.

The record

CVE
CVE-2021-30458
Published
Apr 9, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST National Vulnerability DatabaseAV: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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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