There are several critical vulnerabilities in Microsoft Defender, that put Windows systems at risk. A security researcher has published an 0-day-exploit named BlueHammer on April 3, 2026, that has been patched on April 14, 2026. But there is still an unpatched vulnerability, where the security researcher has published the RedSun exploit. And ther is UnDefend, allowing to stop Windows Defender.
[German]On April 14, 2026 (Patch Day), Microsoft released a fix for Remote Desktop to protect RDP connections against phishing attacks. Users now see a warning message when establishing an RDP connection. This has caused a lot of confusion and issues. I've written a follow-up article providing an overview of the situation, including workarounds. And there are many user comments outlining more insights. Details may be read at my German blog post [use the build-in translator to switch the language].
[English]The security updates KB5083769 and KB5082052 for Windows 11, released on April 14, 2026, are causing BitLocker issues. Microsoft has since confirmed this in updates to the support articles. However, the prompt for the BitLocker recovery key only occurs in specific configurations that are not enabled by default. Details may be read at my German blog post [use the build-in translator to switch the language].
[German]Microsoft has announced an extension of the Extended Security Update (ESU) program for certain legacy software. This includes Microsoft Exchange 2016/2019 and Skype for Business Server, for which ESU "Period 2" is now being launched. This means that organizations can purchase an ESU extension for an additional six months. Details may be read within my German blog post [use the build-in tranlator to switch the language].
On April 14, 2026 (the second Tuesday of the month, Microsoft's Patch Tuesday), Microsoft released cumulative updates for the still-supported client operating system versions of Windows 10 (with an ESU license) and Windows 11. Microsoft has also released security updates for supported Windows Server versions and for Office as well.
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[German]On April 14, 2026, Microsoft released security updates for Windows clients and servers, for Office, and for other products. The security updates address 163 vulnerabilities (CVEs), 8 of which are critical; 2 of these were classified as zero-day vulnerabilities (one of which has been exploited).
[German]Microsoft acknowledged an issue with the reset feature in Windows 11 Enterprise LTSC 2024 on April 9, 2026. If the hotfix KB5079420 from March 10, 2026 (and possibly also the hotfix KB5077212 from February 10, 2026) has been installed, there may be issues with the reset function in Windows 11 Enterprise LTSC 2024. However, the information available to me is somewhat confusing and incomplete. Read more details within my German blog post [use site`s build-in translation to show it in English etc.]
[German]A few hours ago, I reported on a zero-day vulnerability in Adobe Reader. Simply opening a PDF file can be enough to take control of the system. Adobe has now confirmed the vulnerability (CVE-2026-34621) and released a security update to patch it. This should be installed within 72 hours.
[German]Another update from April 3, 2026, affecting Microsoft OneDrive users. On that date, Microsoft announced that starting in May 2026, files deleted from the OneDrive cloud will no longer appear in the local Recycle Bin. However, recovery via the OneDrive or SharePoint web Recycle Bin will still be possible.
[German]Warning to users who use tools such as CPUID, HWMonitor, CPU-Z, etc. and updated it recently (between April 9, and April 10, 2026. The website where these tools were hosted and offered for download has fallen victim to a supply chain attack. As a result, malware was/is being distributed via downloads from the web server. Therefore, anyone who has recently downloaded tools such as CPUID, HWMonitor, CPU-Z, etc., from this website may have malware on their Windows system.
MVP:
2013 – 2016
WIMVP:
2017 – 2020
