October 2021 .NET Updates

The following .NET updates were released in October 2021. This issue will be updated if there are any additional releases during the month.

.NET

* [.NET October 2021 Updates – 5.0.11 and 3.1.20](https://devblogs.microsoft.com/dotnet/october-2021-updates/)
* .NET 5.0.11 and .NET SDK 5.0.402 and .NET SDK 5.0.208 ([Release Notes](https://github.com/dotnet/core/blob/main/release-notes/5.0/5.0.11/5.0.11.md) | [Download](https://dotnet.microsoft.com/download/dotnet/5.0))
* .NET Core 3.1.20 and .NET SDK 3.1.414 and NET SDK 3.1.120 ([Release Notes](https://github.com/dotnet/core/blob/main/release-notes/3.1/3.1.20/3.1.20.md) | [Download](https://dotnet.microsoft.com/download/dotnet-core/3.1))

.NET Framework

* [October 2021 Security and Quality Rollup](https://devblogs.microsoft.com/dotnet/net-framework-october-2021-security-and-quality-rollup/)

.NET Support Policies

Microsoft support policies are defined in the following documents:

* [Microsoft .NET Support Policy](https://dotnet.microsoft.com/platform/support/policy/)
* [.NET Core OS Lifecycle Policy](https://github.com/dotnet/core/blob/master/os-lifecycle-policy.md)

Use the existing issue body as the entry point. Check the linked .NET and .NET Framework release sources for any October 2021 releases, then add missing release links and notes in the same format; done means the month's listed updates are complete and the links work.

Written by the indexing model from the issue text.