CVE-2026-39425 MaxKB: Stored XSS via Unsanitized html_rander Tags in Markdown Rendering
Authenticated users can inject malicious scripts into chatbot prologues, leading to session hijacking and data exposure for visitors.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-39425?
CVE-2026-39425 is a medium-severity cross-site scripting vulnerability in 1Panel-dev MaxKB, published on 14 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
MaxKB is an open-source AI assistant for enterprise. Versions 2.7.1 and below contain a Stored Cross-Site Scripting (XSS) vulnerability that allows authenticated users to inject arbitrary HTML and JavaScript into the Application prologue (Opening Remarks) field by wrapping malicious payloads in <html_rander> tags. The backend fails to sanitize or encode HTML entities in the prologue field when applications are created or updated via the /admin/api/workspace/{workspace_id}/application endpoint, storing the raw payload directly in the database. The frontend then renders this content using an innerHTML-equivalent mechanism, trusting <html_rander>-wrapped content to be safe, which enables persistent DOM-based Stored XSS execution against any visitor who opens the affected chatbot interface. Exploitation can lead to session hijacking, unauthorized actions performed on behalf of victims (such as deleting workspaces or applications), and sensitive data exposure. This issue has been fixed in version 2.8.0.
Weakness: CWE-80
Which versions are affected by CVE-2026-39425?
It affects 1 product.
Products include Maxkb Maxkb.
How do I fix CVE-2026-39425?
No fix has been published for CVE-2026-39425 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-39425 being exploited?
There is no known exploitation of CVE-2026-39425 in the wild and no public exploit code.
Other vulnerabilities in 1Panel-dev MaxKB
- CVE-2025-66419 MaxKB vulnerable to privilege escalation through sandbox bypass
- CVE-2025-66446 MaxKB has a Python sandbox LD_PRELOAD bypass
- CVE-2025-64511 MaxKB has SSRF in sandbox
- CVE-2026-39422 MaxKB has Stored XSS via ChatHeadersMiddleware
- CVE-2026-39423 Stored XSS via Eval Injection in EchartsRander Component
Sources
Also known as GHSA-3rq5-pgm7-pvp4.