In our previous briefings, we dissected the campaigns of UNC6040’s vishing attacks and UNC6395’s supply chain compromise. The common thread weaving through these devastating breaches wasn’t a software zero-day or a brute-forced password; it was the abuse of a legitimate, fundamental component of the modern cloud: the OAuth token.
This isn’t a problem limited to a few threat actors. Throughout 2024 and 2025, a wave of attacks has exploited the core logic of OAuth, allowing adversaries to bypass MFA and breach major corporations like Google, Allianz Life, and Louis Vuitton by tricking users into authorising malicious applications. The attackers don’t need to break in when they can be invited in through a legitimate, token-based handshake.
This is the threat of the OAuth Replay Attack. It’s an attack on the very architecture of trust that connects our cloud applications. To defend against it, you must understand that the target isn’t just your password; it’s the digital key that the password unlocks.
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