Any issues with Pester are fixed in the latest releases, we do not backport fixes to minor releases. We do backport important fixes to 5.x.x. There has been no specific security patches to this date.
Pester uses a small library of C# code that depends on the .NET and .NET Framework. There are currently no known security vulnerabilities with the Pester PowerShell framework.
To report security vulnerabilities in PowerShell, .NET, Windows, or other Microsoft Products & Services, visit the following links: https://www.microsoft.com/en-us/msrc/faqs-report-an-issue https://www.microsoft.com/en-us/msrc/bounty
To report a security vulnerability in Pester framework, email security@pester.dev and ping me on twitter