DeepChat Cross-Site Scripting(XSS) escalate to Remote Code Execution(RCE)

The XSS vulnerability in DeepChat allows an attacker to inject malicious scripts into the application's Mermaid diagram rendering. This injected script can then be executed within the context of the DeepChat application, potentially stealing user credentials, modifying application behavior, or redirecting users to malicious websites. The critical aspect of this vulnerability is the potential for escalation to Remote Code Execution (RCE). By exploiting the Electron IPC bridge, an attacker can register and start a malicious MCP server, effectively gaining control over the application and potentially the underlying system. This represents a significant security risk, particularly in environments where DeepChat is used to process sensitive data or interact with critical systems. The blast radius extends to all users interacting with the Mermaid diagrams within DeepChat.

DeepChat users who rely on the Mermaid diagram rendering functionality are at risk. This includes developers integrating DeepChat into their applications, as well as end-users who interact with DeepChat's interface. Organizations using DeepChat in environments with sensitive data or critical systems are particularly vulnerable.

• javascript / web: Inspect DeepChat application code for instances where user-supplied data is directly incorporated into Mermaid diagrams without proper sanitization. • javascript / web: Monitor network traffic for suspicious requests related to Electron IPC communication, particularly those involving MCP server registration. • javascript / web: Review DeepChat logs for any errors or warnings related to script execution or unexpected behavior within the Mermaid diagram renderer. • generic web: Use curl/wget to test for the ability to inject JavaScript into Mermaid diagrams via URL parameters or form fields.

1. 2025-12-03Disclosure

   disclosure

1. Reserviert2025-11-24
2. Veröffentlicht2025-12-03
3. EPSS aktualisiert2026-03-23

The primary mitigation for CVE-2025-66222 is to immediately upgrade DeepChat to version 0.5.0 or later, which contains the fix for the XSS vulnerability. If upgrading is not immediately feasible, consider implementing temporary workarounds. Input sanitization on user-provided data used in Mermaid diagrams can help prevent the injection of malicious scripts. Restrict access to the Electron IPC bridge to only trusted sources. Monitor DeepChat logs for suspicious activity, particularly related to MCP server registration and execution. After upgrading, confirm the fix by attempting to inject a simple JavaScript payload into a Mermaid diagram and verifying that it is not executed.