Microsoft software and cloud platforms underpin enterprise systems, so vulnerabilities and security advisories can affect identity, data, and operations.
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Background for this topic.
Microsoft is a technology company whose Windows, Microsoft 365, Azure, identity services, and developer tools form a widely deployed enterprise computing ecosystem. Its security relevance spans endpoint and server software, cloud control planes, authentication, collaboration data, and the update mechanisms used to maintain them.
Security news under this tag commonly concerns vulnerabilities requiring patching, exploits against exposed services, identity or token compromise, and misconfiguration of cloud permissions or authentication policies. Practitioners should verify affected versions and exposure, apply updates or mitigations, enforce multifactor authentication and least privilege, and monitor relevant audit logs. Incidents involving Microsoft-hosted identities or data may require rapid session and credential containment, investigation across cloud and on-premises systems, and assessment of privacy or regulatory obligations.
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ACR Stealer, an infostealer in circulation since 2024, is walking out of enterprise networks with saved browser passwords, live session tokens, PDFs, Microsoft 365 documents, and files from synced OneDrive and SharePoint folders
From late April 2026 to mid-June 2026, Microsoft Defender Experts observed increased ACR Stealer activity across customer environments. These campaigns are successfully using ClickFix lures to steal browser credentials, authentication tokens, and sensitive documents from enterprise environments. The post ACR Stealer: Two observed intrusion chains amid increased threat activity appeared first on Microsoft Security Blog.