Microsoft-Defender

Microsoft Defender and Purview Add AI Agent Controls in September 2026

FIRST LOOK ATLAS OWASP MEDIUM ▲ 7.2 Microsoft Security Blog Sep 25, 2026

Microsoft's September 2026 security update delivers network-layer data loss prevention for agentic AI traffic, AI-generated email detonation summaries in Security Copilot, and enterprise-scale labelling automation in Microsoft Purview. These capabilities close a material gap for defenders by extending Zero Trust policy enforcement to on-behalf-of (OBO) agent actions — an emerging blind spot as autonomous agents operate across employee devices and cloud platforms. Residual gaps remain around coverage breadth for third-party agent frameworks, cross-platform policy portability, and the organisational maturity required to define reliable classification policies before enforcement becomes effective.

Microsoft Sentinel and Defender Experts Add Multi-Cloud MDR Coverage

FIRST LOOK ATLAS OWASP MEDIUM ▲ 6.5 Microsoft Security Blog Aug 28, 2026

Microsoft's August 2026 security update extends Defender Experts MDR to third-party data sources ingested via Sentinel — including Palo Alto Networks, AWS, and Okta — and introduces Entra Tenant Governance for centralised multi-tenant visibility and drift monitoring. These additions close a meaningful gap for organisations running hybrid or multi-cloud environments, where managed detection historically stopped at Microsoft-native telemetry boundaries. Realising the full benefit requires P2 licensing, mature Sentinel ingestion pipelines, and organisational readiness to act on cross-tenant configuration drift alerts.

Microsoft 365 Copilot Prompt Injection Threats in Enterprise

ATLAS OWASP MEDIUM ▲ 6.5 Microsoft Security Blog Jun 10, 2026

Microsoft has released a structured investigator playbook for reconstructing AI-related activity across Microsoft 365 Copilot and Azure AI services, addressing the challenge of converting raw telemetry into coherent incident timelines. The playbook targets threats already observed in enterprise deployments, including prompt injection attempts and unauthorized data access, and operationalizes a scope–context–signal methodology across Purview, Defender, and Sentinel. This guidance directly supports security teams responding to AI-specific incidents where unstructured telemetry has previously hindered attribution and impact assessment.

Anthropic Claude Code Prompt Injection Leaks Secrets

ATLAS OWASP HIGH ▲ 9.1 Microsoft Security Blog Jun 08, 2026

Microsoft Threat Intelligence disclosed a vulnerability in Anthropic's Claude Code GitHub Action whereby prompt injection via untrusted GitHub content — issue bodies, PR descriptions, and comments — could cause the AI agent to read sensitive environment variables, including the ANTHROPIC_API_KEY, from /proc/self/environ. The flaw stemmed from inconsistent sandboxing: while subprocess execution paths like Bash were scrubbed of environment variables, the Read tool had no equivalent restriction. Anthropic patched the issue in Claude Code version 2.1.128 by blocking access to sensitive /proc filesystem paths.

Microsoft-Defender