CVE-2026-40568Public exploitNetwork attack vector

Stored XSS via incomplete signature sanitization

Published Apr 21, 2026 · Updated Apr 21, 2026

Stored XSS in FreeScout before 1.8.213 allows remote authenticated users with signature permission to inject persistent HTML. Helper::stripDangerousTags blocks only four element types and preserves event-handler attributes before the signature is stored, emitted as raw HTML, and inserted into the visible DOM. The delegatable mailbox permission is sufficient, and opening a conversation triggers the content without victim interaction, enabling phishing or browser script execution where CSP does not block it.

CVSS severity8.5
High
EPSS probability0.24%
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 FreeScout before 1.8.213 allows remote authenticated users with signature permission to inject persistent HTML. Helper::stripDangerousTags blocks only four element types and preserves event-handler attributes before the signature is stored, emitted as raw HTML, and inserted into the visible DOM. The delegatable mailbox permission is sufficient, and opening a conversation triggers the content without victim interaction, enabling phishing or browser script execution where CSP does not block it.

The record

CVE
CVE-2026-40568
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
FreeScout
Product
FreeScout
Classifications
CWE-79, CWE-116, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 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=< 1.8.213

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

FreeScout · FreeScoutversion=< 1.8.213

Published CVSS scores

8.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/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')
CWE-116Improper Encoding or Escaping of Output
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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