Analysis · curated 31 Aug 2026
Block Prompt Injection Emails with Microsoft Defender
First reported o365reports.com
Coverage timeline
Single-source analysis — first reported, latest, and curated coincide.
Why it matters
Email-based prompt injection lets attackers target AI assistants that summarize and act on inbox content, so defenders benefit from understanding how Microsoft Defender now quarantines and surfaces these messages.
O365Reports explains a new Prompt Injection Protection capability in Microsoft Defender for Office 365 that detects and blocks emails containing malicious instructions aimed at manipulating AI assistants (such as Microsoft 365 Copilot) during mail flow. The post covers how email prompt injection differs from phishing, its impact, and how to track quarantined injection emails via Threat Explorer and KQL Advanced Hunting.