# CVE-2025-66481: DeepChat's Incomplete XSS Fix Allows RCE through Mermaid Content

> Attackers can achieve remote code execution on victim machines via XSS in DeepChat's Mermaid content rendering due to insufficient sanitization.

- **Severity:** Critical 9.7 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Dec 2025
- **Updated:** 9 Dec 2025
- **Also known as:** GHSA-h9f5-7hhf-fqm4

## What is CVE-2025-66481?

CVE-2025-66481 is a critical cross-site scripting vulnerability in ThinkInAIXYZ deepchat, published on 9 Dec 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

DeepChat is an open-source AI chat platform that supports cloud models and LLMs. Versions 0.5.1 and below are vulnerable to XSS attacks through improperly sanitized Mermaid content. The recent security patch for MermaidArtifact.vue is insufficient and can be bypassed using unquoted HTML attributes combined with HTML entity encoding. Remote Code Execution is possible on the victim's machine via the electron.ipcRenderer interface, bypassing the regex filter intended to strip dangerous attributes. There is no fix at time of publication.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-80 (Improper Neutralization of Script-Related HTML Tags in a Web Page), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2025-66481?

It affects 1 product.


Products: Thinkinai Deepchat.

## How do I fix CVE-2025-66481?

No fix has been published for CVE-2025-66481 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-66481 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66481 exists.

## Other vulnerabilities in ThinkInAIXYZ deepchat

- [CVE-2025-67744](https://insights.sbomify.com/CVE-2025-67744/): Mermaid XSS vulnerability leads to Remote Code Execution (critical 9.7)
- [CVE-2025-66222](https://insights.sbomify.com/CVE-2025-66222/): DeepChat Cross-Site Scripting(XSS) escalate to Remote Code Execution(RCE) (critical 9.7)
- [CVE-2025-58768](https://insights.sbomify.com/CVE-2025-58768/): DeepChat's Mermaid rendering has XSS leading to RCE (critical 9.7)
- [CVE-2025-55733](https://insights.sbomify.com/CVE-2025-55733/): DeepChat One-click Remote Code Execution through Custom URL Handling (critical 9.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66481 and fix it if it is affected.

What it is: CVE-2025-66481 is a critical cross-site scripting vulnerability in ThinkInAIXYZ deepchat, published on 9 Dec 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66481 exists.

Affected product: ThinkInAIXYZ deepchat. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-66481/ (Markdown: https://insights.sbomify.com/CVE-2025-66481/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66481
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66481
- OSV: https://osv.dev/vulnerability/CVE-2025-66481

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-66481/
Summaries are generated and may contain mistakes; the official description above is the record.