Silent HMAC Key Contamination: Uncovering a Logic Flaw in Burp's JWT Editor Extension

This story was originally published on HackerNoon at: https://hackernoon.com/silent-hmac-key-contamination-uncovering-a-logic-flaw-in-burps-jwt-editor-extension.

JWT Editor was shortlisted for “Best Auth & Access Control” in PortSwigger’s 2026 Burp Suite Extension Awards. This is the story of finding a silent bug inside.

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JWT Editor was shortlisted for “Best Auth & Access Control” in PortSwigger’s 2026 Burp Suite Extension Awards. This is the story of finding a silent bug inside.