.NET 8/9 support ends Nov 10, 2026; Windows Server 2012 ESU ends Oct 13. What each deadline covers, the 2012 R2 to 2025 direct in-place upgrade, and how to track both.
A regression in cryptographic signature validation introduced a CVSS 9.1 flaw into .NET 10.0. The Data Protection API implemented HMAC verification incompletely, opening the door to padding oracle attacks and forged authentication tokens.
Union types land in C# 15 with .NET 11 Preview 2. A look at the design, exhaustive pattern matching, internal implementation, comparison with unions in other languages, and practical use in Blazor and Minimal API.
