Lab: Same Site Strict bypass via sibling domain
Summary: PortSwigger's lab demonstrates a cross-site WebSocket hijacking attack in which the live chat feature's handshake request carries no unpredictable tokens, so a script can open a new chat connection and pull the full chat history. Because the site sets session cookies with SameSite=Strict, the attack is delivered through a reflected XSS on a sibling domain, cms-YOUR-LAB-ID.web-security-academy.net, which the browser treats as same-site and therefore sends the victim's session cookie with the WebSocket request.
What's compelling: The chat history contains the victim's login credentials in plain text, so a single reflected XSS on a sibling domain is enough to turn a SameSite=Strict cookie into full account takeover.
Read the original at PortSwigger Research ↗
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