Stored XSS in n8n Form Trigger allows Account Takeover via injected iframe and video/source

Vulnerability Description

n8n is a workflow automation platform. From 1.77.0 to before 1.98.2, a stored Cross-Site Scripting (XSS) vulnerability was identified in n8n, specifically in the Form Trigger node's HTML form element. An authenticated attacker can inject malicious HTML via an <iframe> with a srcdoc payload that includes arbitrary JavaScript execution. The attacker can also inject malicious Javascript by using <video> coupled <source> using an onerror event. While using iframe or a combination of video and source tag, this vulnerability allows for Account Takeover (ATO) by exfiltrating n8n-browserId and session cookies from authenticated users who visit a maliciously crafted form. Using these tokens and cookies, an attacker can impersonate the victim and change account details such as email addresses, enabling full control over the account—especially if 2FA is not enabled. Users should upgrade to version >= 1.98.2.

References

• https://github.com/n8n-io/n8n/security/advisories/GHSA-hfmv-hhh3-43f2
• https://github.com/n8n-io/n8n/pull/16329
• https://github.com/n8n-io/n8n/commit/7940384a85041a1890b1203d69c092c887312500