{"id":"GHSA-w5cr-2qhr-jqc5","summary":"Cloudflare Agents has a Reflected Cross-Site Scripting (XSS) vulnerability in AI Playground site","details":"## Summary\n\nA 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.\n\n### Root cause\n\nThe 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 `\u003cscript\u003e` tag.\n\n### Impact\n\nAn attacker could craft a malicious link that, when clicked by a victim, would:\n- Steal user chat message history \n- Access all LLM interactions stored in the user's session.\n- Access connected MCP Servers \n- 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\n\n### Mitigation:\n\n- PR: https://github.com/cloudflare/agents/pull/841\n- Agents-sdk users should upgrade to `agents@0.3.10`\n- Developers using `configureOAuthCallback` with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.\n\n### Credits\n\nDisclosed responsibly by Nishant Kumawat","modified":"2026-02-13T21:10:51.108736Z","published":"2026-02-13T21:04:00Z","database_specific":{"cwe_ids":["CWE-79"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-02-13T21:04:00Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/cloudflare/agents/security/advisories/GHSA-w5cr-2qhr-jqc5"},{"type":"WEB","url":"https://github.com/cloudflare/agents/pull/841"},{"type":"WEB","url":"https://github.com/cloudflare/agents/commit/3f490d045844e4884db741afbb66ca1fe65d4093"},{"type":"PACKAGE","url":"https://github.com/cloudflare/agents"}],"affected":[{"package":{"name":"agents","ecosystem":"npm","purl":"pkg:npm/agents"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.3.10"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-w5cr-2qhr-jqc5/GHSA-w5cr-2qhr-jqc5.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N"}]}