GHSA-w5cr-2qhr-jqc5
Cloudflare Agents has a Reflected Cross-Site Scripting (XSS) vulnerability in AI Playground site
Quick fix
GHSA-w5cr-2qhr-jqc5 — agents: upgrade to the fixed version with the command below.
npm install agents@0.3.10Details
## Summary
A Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The error_description query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.
### Root cause
The OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `<script>` tag.
### Impact
An attacker could craft a malicious link that, when clicked by a victim, would: - Steal user chat message history - Access all LLM interactions stored in the user's session. - Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf
### Mitigation:
- PR: https://github.com/cloudflare/agents/pull/841 - Agents-sdk users should upgrade to `agents@0.3.10` - Developers using `configureOAuthCallback` with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.
### Credits
Disclosed responsibly by Nishant Kumawat
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