IT Daily Roundup – September 17, 2026
1. September Windows Patch KB5124008 Breaks Domain Login
Microsoft is investigating a serious issue with the KB5124008 update from this month's Patch Tuesday (September 9th): on a subset of Windows 11 25H2 devices, after installation and reboot, domain login stops working entirely. Affected computers lose their secure channel with Active Directory, leaving employees locked out with authentication errors — despite entering correct credentials. The root cause is the new Machine Identity Isolation (MII) security feature, which incorrectly evaluates machine identity when running in enforce or audit mode. A temporary workaround involves setting the registry value MachineIdentityIsolation to 0 under HKLM\SYSTEM\CurrentControlSet\Control\Lsa, rebooting, and then running Test-ComputerSecureChannel -Repair -Credential(Get-Credential) in an elevated PowerShell session. Microsoft has not yet released an official fix.
Why it matters: For a business where employees boot up their computers in the morning and cannot log in to the domain, this is effectively a total workstation outage. KB5124008 also contained patches for actively exploited zero-day vulnerabilities, putting IT teams in the classic dilemma of "patch and risk an outage, or hold and remain exposed." If your organization runs Windows 11 25H2 in a domain environment, we recommend backing up the registry before deployment and preparing a recovery procedure — or holding the patch until Microsoft issues a fix.
2. Chrome and Firefox Patch 115 Security Vulnerabilities Combined
Google released Chrome 153 (versions 153.0.8010.47/48 for Windows and macOS) with fixes for 42 vulnerabilities, including 3 critical ones (out-of-bounds read in WebGL and use-after-free bugs in Internals and Workers components) and 28 high-severity issues. Mozilla simultaneously released Firefox 156, addressing 73 vulnerabilities including 29 high-severity problems — sandbox escape, site isolation weaknesses, and privilege escalation. The updates also cover Thunderbird 156/140.16 and Firefox ESR. None of the patched vulnerabilities has been reported as actively exploited in the wild.
Why it matters: The browser is today the primary gateway to most business applications — webmail, ERP, banking portals, and remote access tools all run inside a browser window. A critical WebGL flaw or use-after-free bug can allow an attacker to execute arbitrary code simply by getting a user to visit a malicious page. Since none of these vulnerabilities is currently being actively exploited, there is a comfortable window to deploy the update in a planned, controlled way through endpoint management or MDM — ideally today, before that changes.
3. Parallels Desktop Lets Non-Admin Mac Users Gain Root Access — Intel Macs Have No Fix
Security researchers disclosed CVE-2026-90894 (CVSS 7.8) in Parallels Desktop 26 and earlier, dubbed "ParaShells." The flaw involves argument injection during VM appliance installation — an unprivileged Mac user can pass crafted arguments to execute code as root, effectively taking full control of the host system. A fix is available in Parallels Desktop 27.0.0, but Parallels 27 requires a Mac with Apple Silicon (M1 or newer) and macOS Sonoma 14.7 or later. Users on Intel Macs cannot upgrade to version 27, and Parallels has not confirmed whether a fix will be backported to version 26.
← All postsWhy it matters: Parallels Desktop is commonly used in businesses where employees need Windows applications on Macs — and in those hybrid environments, a root access flaw in the virtualization layer is particularly dangerous, since an attacker can move from the VM host into files and processes outside the VM. If your organization runs older Intel Macs with Parallels, we recommend restricting user permissions to the minimum necessary or exploring alternative solutions. Migrating to Apple Silicon Macs addresses this issue while delivering other performance and security benefits.