CVE-2021-25978Network attack vector

Stored XSS via unsanitized SVG attachments

Published Nov 7, 2021 · Updated Apr 30, 2025

Stored XSS in ApostropheCMS 2.63.0 through 3.3.1 allows remote authenticated users to execute JavaScript via an uploaded SVG image. The Images module accepts SVG attachments without sanitizing embedded active content, and its direct-view media link serves that content to a browser. An editor with SVG upload permission must store the file and a victim must open it directly; normal img-tag rendering ignores the payload.

CVSS severity5.4
Medium
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in ApostropheCMS 2.63.0 through 3.3.1 allows remote authenticated users to execute JavaScript via an uploaded SVG image. The Images module accepts SVG attachments without sanitizing embedded active content, and its direct-view media link serves that content to a browser. An editor with SVG upload permission must store the file and a victim must open it directly; normal img-tag rendering ignores the payload.

The record

CVE
CVE-2021-25978
Published
Nov 7, 2021
Updated
Apr 30, 2025
Vendor
Apostrophe Technologies
Product
ApostropheCMS
Classifications
CWE-79
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2025Record 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=2.63.0 <unspecified
  2. Affected versionversion=unspecified <=3.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Apostrophe Technologies · ApostropheCMSversion=2.63.0 <unspecified; version=unspecified <=3.3.1

Published CVSS scores

5.4MendCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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