freescout-help-desk freescout up to 1.8.212 Conversation app/Misc/Helper.php stripDangerousTags cross site scripting

Summaryinfo

A vulnerability was found in freescout-help-desk freescout up to 1.8.212. It has been classified as problematic. Impacted is the function Helper::stripDangerousTags of the file app/Misc/Helper.php of the component Conversation Handler. The manipulation leads to cross site scripting. This vulnerability is uniquely identified as CVE-2026-40568. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in freescout-help-desk freescout up to 1.8.212. This issue affects the function Helper::stripDangerousTags of the file app/Misc/Helper.php of the component Conversation Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. The summary by CVE is:

FreeScout is a free self-hosted help desk and shared mailbox. Versions prior to 1.8.213 have a stored cross-site scripting (XSS) vulnerability in the mailbox signature feature. The sanitization function `Helper::stripDangerousTags()` (`app/Misc/Helper.php:568`) uses an incomplete blocklist of only four HTML tags (`script`, `form`, `iframe`, `object`) and does not remove event handler attributes. When a mailbox signature is saved via `MailboxesController::updateSave()` (`app/Http/Controllers/MailboxesController.php:267`), HTML elements such as ``, ``, and `` with event handler attributes like `onerror` and `onload` pass through sanitization unchanged and are stored in the database. The signature is then rendered as raw HTML via the Blade `{!! !!}` tag in `editor_bottom_toolbar.blade.php:6` and re-inserted into the visible DOM by jQuery `.html()` at `main.js:1789-1790`, triggering the injected event handlers. Any authenticated user with the `ACCESS_PERM_SIGNATURE` (`sig`) permission on a mailbox -- a delegatable, non-admin permission -- can inject arbitrary HTML and JavaScript into the mailbox signature. The payload fires automatically, with no victim interaction, whenever any agent or administrator opens any conversation in the affected mailbox. This enables session hijacking (under CSP bypass conditions such as IE11 or module-weakened CSP), phishing overlays that work in all browsers regardless of CSP, and chaining to admin-level actions including email exfiltration via mass assignment and self-propagating worm behavior across all mailboxes. Version 1.8.213 fixes the issue.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-40568 since 04/14/2026. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

By approaching the search of inurl:app/Misc/Helper.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 1.8.213 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 1d83e1cffb0bf8d109625313530b36b0f5910b3f is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• freescout-help-desk

Name

• freescout

Version

• 1.8.212

License

• open-source

Website

• Product: https://github.com/freescout-help-desk/freescout/

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• 🔒

CPE 2.2info

• 🔒

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