Microsoft had a bug in the .NET Framework in the July update. Recently, Microsoft released a fix for the bug.
In July, Microsoft released a Windows Patch Tuesday update that included a fix for the .NET Framework security feature bypass vulnerability (see CVE-2018-8356), and Microsoft admitted on July 20 that it knew the update was generated. The .NET Framework bug will cause the application to fail to start or not function properly, so Microsoft decided to entirely revoke the update to prevent more systems from being affected by the issue.
“If you installed the July 2018 update and have not yet seen any negative behavior, we recommend that you leave your systems as-is but closely monitor them and ensure that you apply upcoming .NET Framework updates,” Microsoft said in the July 20 advisory.
On July 30, Microsoft released a fix for all affected versions of the .NET Framework, and Microsoft recommended that computers affected by the bug install updates as soon as possible. It said: “Today, we released the July 2018 update, which fixes the .NET Framework 2.0, 3.5, 3.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1 and 4.7. If you are experiencing a problem known in Knowledge Base article 4435913, we recommend that you apply this update.
It’s worth noting that this update will not be automatically sent to the Windows system via Windows Update, but will only be provided as a manual download in the Microsoft Update Catalog, which users need to choose.