CVE-2021-39250Public exploitNetwork attack vector

Administrator compromise via iframe whitelist bypass

Published Aug 17, 2021 · Updated Aug 4, 2024

Stored XSS in Invision Community before 4.6.5.1 allows remote authenticated users to execute JavaScript through a crafted post or message. The content parser permits same-site iframe sources and accepts a /core/../uploads path, causing an attacker-controlled HTML attachment to execute in readers' origins. Exploitation requires a forum account and a victim to view the content; administrator interaction can expose credentials or a session and enable server-side code execution.

CVSS severity5.4
Medium
EPSS probability0.81%
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 Invision Community before 4.6.5.1 allows remote authenticated users to execute JavaScript through a crafted post or message. The content parser permits same-site iframe sources and accepts a /core/../uploads path, causing an attacker-controlled HTML attachment to execute in readers' origins. Exploitation requires a forum account and a victim to view the content; administrator interaction can expose credentials or a session and enable server-side code execution.

The record

CVE
CVE-2021-39250
Published
Aug 17, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1190Exploit Public-Facing Application

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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