GHSA-9f4f-jv96-8766: Open WebUI vulnerable to stored XSS via unescaped markdown token in MarkdownTokens.svelte leading to full account takeover and RCE via functions

Summary A vulnerability in the way certain html tags in chat messages are rendered allows attackers to inject JavaScript code into a chat transcript. The JavaScript code will be executed in the user's browser every time that chat transcript is opened, allowing attackers to retrieve the user's access token and gain full control over their account. Chat transcripts can be shared with other users in the same server, or with the whole open-webui community if "Enable Community Sharing" is enabled in the admin panel. If this exploit is used against an admin user, it is possible to achieve Remote Code Execution on the server where the open-webui backend is hosed. This can be done by creating a new function which contains maliicious python code. **This vulnerability also affects chat transcripts uploaded to https://openwebui.com/c/<user>/<chat_id>, allowing for wormable stored XSS in https://openwebui.com** Details Stored XSS The file https://github.com/open-webui/open-webui/blob/main/src/lib/components/chat/Messages/Markdown/MarkdownTokens.svelte#L269-L279 contains the following code: {:else if token.text.includes(<iframe src="${WEBUI_BASE_URL}/api/v1/files/)} {@html ${token.text}} That code checks if a chat message has an html tag which contains the text <iframe src="${WEBUI_BASE_URL}/api/v1/files/, and if so, it renders that html tag using {@html}, which is a dangerous Svelte functionality that allows text to be rendered as HTML code. Attackers can abuse this by sending a chat message with the following payload: <iframe src="http://localhost:8080/api/v1/files/" onload="alert(1)"></iframe>, where http://localhost:8080 is the URL where the open-webui backend server is hosted. This will cause a JavaScript alert window to be displayed every time that chat transcript is opened. image image In a real attack scenario, instead of injecting alert(1) in the onload attribute, attackers can use the following code to steal the user's access token and send it to a server t