How exploitable is this vulnerability in real deployments?

The vulnerability is highly exploitable in environments where non-admin users can edit mailbox signatures. Once a user with the signature permission injects a payload, the script runs automatically for any agent or administrator who opens a conversation in that mailbox, without requiring them to click or interact with the malicious content.

Does an attacker need administrator access to exploit this issue?

No. Exploitation only requires an authenticated account with the `ACCESS_PERM_SIGNATURE` (`sig`) permission on a mailbox. This permission is delegatable and does not require full administrative privileges, meaning lower-privileged users can introduce the malicious signature.

What is the safest general fix pattern for this vulnerability class?

The most robust fix is to combine strict, allowlist-based sanitization with context-aware output encoding: - Use a mature HTML sanitization library configured to allow only a minimal set of safe tags and attributes and to strip all script-capable constructs. - Remove reliance on unescaped template directives and avoid inserting user-derived HTML using `.html()` or similar APIs. - Where possible, treat signatures as plain text or constrained markup that is always encoded before rendering.

Severity:

HIGH RISK

(8.5)

Stored Cross-Site Scripting (CWE-79) in FreeScout Mailbox Signatures

CVE-2026-40568

Published:

Apr 21, 2026

Status:

Deferred

Summary

Affected Context

Exploit Preconditions

Why This Happens

Potential Impact

General Mitigation Guidance

How Teams Detect Issues Like This

Frequently Asked Questions

Source

NDV

Recent Vulnerabilities

CWE-74;CWE-89

HIGH RISK

HIGH

(7.3)

SQL Injection via Unsanitized ID Parameter (CWE-89) in Pharmacy Sales and Inventory System /ajax.php

Database Compromise and Data Integrity Loss

April 27, 2026

CWE-863

HIGH RISK

HIGH

(8.5)

Incorrect Authorization (CWE-863) in OpenClaw chat.send Session Management

Privilege Escalation and Unauthorized Session Control

April 27, 2026

Vulnerability Type

Category:

Stored Cross-Site Scripting (XSS)

CWE:

CWE-79;CWE-116

Impact:

Account Compromise and Privilege Escalation via Stored XSS

Severity:

HIGH RISK

(8.5)

CVSS Version:

3.1

Vulnerability Type

Category:

Stored Cross-Site Scripting (XSS)

CWE:

CWE-79;CWE-116

Impact:

Account Compromise and Privilege Escalation via Stored XSS

Severity:

HIGH RISK

(8.5)

CVSS Version:

3.1

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Ask AI for summary of CodeAnt

Stored Cross-Site Scripting (CWE-79) in FreeScout Mailbox Signatures

Summary

Affected Context

Exploit Preconditions

Why This Happens

Potential Impact

General Mitigation Guidance

How Teams Detect Issues Like This

Frequently Asked Questions

Source

Recent Vulnerabilities

HIGH RISK

HIGH

(7.3)

SQL Injection via Unsanitized ID Parameter (CWE-89) in Pharmacy Sales and Inventory System /ajax.php

HIGH RISK

HIGH

(8.5)

Incorrect Authorization (CWE-863) in OpenClaw chat.send Session Management

Vulnerability Type

Vulnerability Type

Vulnerability Type

Catch This CVE While Code Is Being Written

Ship clean & secure code faster

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