A Microsoft 365 email security-control bypass that lets attackers submit unauthenticated messages posing as internal users by leaving one SMTP field blank. The technique targets Exchange Online’s RejectDirectSend setting and does not represent a vulnerability in Microsoft software or in ReliaQuest systems; instead, it exposes a limitation in how the control evaluates Direct Send traffic. […]

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Mayura Kathir

Source: gbHackers
Source Link: https://gbhackers.com/microsoft-365-security-bypass/