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Microsoft Exchange Server

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high advisory

Microsoft Security Updates — July 2026

Roundup of Microsoft security advisories published in July 2026.

PoC PowerShell +516 roundup
10c 227i updated
medium threat

Suspicious File Creation by Microsoft Exchange Unified Messaging Service

This rule detects suspicious file creations by the Microsoft Exchange Server Unified Messaging service, potentially indicative of exploitation of CVE-2021-26858, leading to web shell deployment for initial access, lateral movement, and persistence.

exploited Microsoft Exchange Server exchange webshell cve-2021-26858 initial-access
2r 3t 1c
medium threat

Exchange PowerShell Used to Add New ActiveSync Allowed Device

An adversary may use the Exchange PowerShell cmdlet, Set-CASMailbox, to add a new ActiveSync allowed device, potentially gaining persistent access to a user's email and sensitive information.

exploited Microsoft Exchange Server exchange powershell activesync persistence
2r 3t