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Update your firewall rules: Teams and Copilot are changing address
Microsoft is redirecting Microsoft 365 and Teams web users to new *.cloud.microsoft domains, requiring firewall and proxy rule updates by early October.
Starting September 2026, Microsoft is redirecting M365 web users to copilot.cloud.microsoft and Teams web users to teams.cloud.microsoft, announced via MessageCenter posts MC1465764 and MC1462915. All redirects should complete by early October 2026, with limited Teams exceptions possible until December 31, 2026. Microsoft advises reviewing client, proxy, firewall, and secure web gateway configurations, and suggests using TenantRestrictions to control personal Microsoft account access instead of blocking the new Copilot address.
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Microsoft security advisory – September 2026 monthly rollup (AV26-896) – Update 1
Canada's Cyber Centre relays Microsoft's September 2026 rollup; CISA added exploited zero-days CVE-2026-85880 and CVE-2026-81963 to KEV.
Advisory AV26-896 from the Canadian Centre for Cyber Security summarizes Microsoft's September 2026 monthly security rollup, listing affected products across Windows, Office, .NET, Azure, Exchange and SQL Server. It notes Microsoft confirmed CVE-2026-81963 and CVE-2026-85880 have been exploited. On September 8, 2026, CISA added both CVEs to its Known Exploited Vulnerabilities catalog, and administrators are urged to apply the updates.
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Microsoft Releases Emergency Patch to Fix RDS Snafu
Microsoft's out-of-band KB5129195 fixes September Patch Tuesday regressions breaking RDS connections, Hyper-V shared folders, and USB audio.
Microsoft released cumulative out-of-band update KB5129195 on September 14, 2026, fixing RDS instability causing failing RDP connections, sign-in issues, and hanging servers. The patch also resolves Hyper-V Plan9 shared-folder failures affecting WSL and Claude Cowork, plus USB Audio Class 1.0 device failures. This is Microsoft's sixth emergency patch after a September Patch Tuesday that fixed a record 974 CVEs.
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Microsoft Confirms Remote Desktop Services Might Stop Working Following Sept. 2026 Security Update
Microsoft's September 2026 Patch Tuesday updates (KB5124008) can break Remote Desktop Services, causing RDP failures and freezes across Windows clients and servers.
Microsoft confirmed its September 2026 security updates, including KB5124008 for Windows 11 24H2/25H2, introduced a reliability regression where RDP connections fail after several minutes and servers hang at the 'Please wait for the Remote Desktop Configuration' screen. MMC, RDS Licensing Diagnoser, File Explorer, and the Windows Update settings page may also stop responding. The issue affects Windows 10/11 clients and Windows Server 2012 through 2025; Microsoft marked it Mitigated on September 11 and is developing a permanent fix, with VM restart offered as a temporary workaround.
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Microsoft Confirms KB5002914 Update Breaks Copy and Paste on Excel
Microsoft confirms KB5002914 Excel security update silently breaks copy-paste in Excel 2016-2024, forcing admins to choose between usability and security fixes.
Microsoft added a known issue to KB5002914, the September 8, 2026 Excel security update, where paste, autofill, and formula dragging fail silently with no error in Excel 2016, 2019, 2021, and 2024. The update addresses remote code execution and information disclosure flaws including CVE-2026-81399, CVE-2026-81390, and CVE-2026-81954. No hotfix date has been published as of September 15, 2026; the only widely confirmed recovery is uninstalling or rolling back KB5002914, which drops the month's Excel security fixes.
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SolarWinds Database Mapper and Task Factory enable data professionals to accelerate cloud migrations
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CISA Red Team Fully Compromised Two Critical Infrastructure Orgs
CISA red teams achieved full domain and cloud compromise at two critical infrastructure orgs; one SOC never detected the intrusion.
CISA advisory AA26-237A documents two simultaneous red team assessments. Organization A (Government Services sector) missed the intrusion entirely, as default credentials on a web app, ADCS ESC1 abuse, and thousands of false-positive alerts let the red team reach sensitive business systems and read SOC email. Organization B (Water/Wastewater sector) detected, isolated, and reimaged hosts quickly, but both orgs lacked Conditional Access for workload identities, and B still exposed DCSync, Golden Ticket, and OT network attack paths.
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Water sector passes, government sector fails attempts to spot and halt simulated CISA attack
CISA red teamers compromised both a government and a water organization; water defenders detected and contained the simulated attack, government defenders did not.
CISA's red team gained initial access, elevated domain privileges, and lateral movement into sensitive business systems and cloud resources at an unnamed government organization, whose SOC ignored low- and medium-severity EDR alerts buried under thousands of false positives. A water organization's SOC quarantined phishing-compromised workstations within 2, 10, and 20 minutes, and later detected and isolated intrusions reaching the OT DMZ bastion host. Both organizations underestimated cloud risk, lacked Microsoft Conditional Access for workload identities, and had no process to revoke compromised access and refresh tokens. This is one of CISA's rare public red-team reports since 2023.
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Microsoft Patch Tuesday for August 2026 Fixed a Zero
Microsoft's August 2026 Patch Tuesday fixes 398 CVEs, including an actively exploited WinSock zero-day CVE-2026-68820 and wormable DNS RCE CVE-2026-62878.
Microsoft's August 2026 Patch Tuesday addresses 398 CVEs across Windows, Office, Azure, Exchange Server, SharePoint, Teams, .NET and other products, with 62 rated Critical. The actively exploited CVE-2026-68820 is a use-after-free in the Windows WinSock afd.sys driver that can yield SYSTEM privileges via a race condition. CVE-2026-62878 is a critical, wormable stack buffer overflow in Windows DNS Server allowing unauthenticated, remote code execution without user interaction. Other notable fixes include WDS TFTP RCE CVE-2026-62893, a QUIC flaw affecting roughly 13.5 million sites (CVE-2026-62815), an Exchange authentication bypass EoP demonstrated at Pwn2Own Berlin (CVE-2026-62911), and two TPM 2.0 reference implementation fixes.
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September 2026 Patch Tuesday: Record patch count, 2 zero-days, and a SigRed successor
Microsoft's September 2026 Patch Tuesday delivers a record patch count, fixing two exploited zero-days and a wormable DNS flaw dubbed a SigRed successor.
Microsoft's September 2026 Patch Tuesday sets another record patch count, fixing two vulnerabilities exploited as zero-days: CVE-2026-81963, a Windows Update Stack low-privilege-to-SYSTEM escalation reported by MSTIC, and CVE-2026-85880, a Windows Advanced Local Procedure Call escalation reported by Proofpoint. Zero Day Initiative's Dustin Childs urges priority on a cluster of 20 potentially wormable bugs including DNS RCE CVE-2026-69730, described as a spiritual successor to SigRed, plus Kerberos authentication bypass CVE-2026-69676 that could give any authenticated domain user RCE on domain controllers, and Exchange RCE CVE-2026-55007 via a malicious Visio attachment. All Windows fixes are bundled in cumulative updates, and experts stress prioritizing exploitable, reachable flaws over raw patch counts.
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