An XML External Entity attack (Or XXE for short) is a type of attack that exploits weaknesses (Or more so features) in how external entities are loaded when parsing XML in code. This repository checks which XML Parsing methods available in .NET Core are vulnerable to this sort of attack.
Full blog post here : https://dotnetcoretutorials.com/2021/01/11/testing-xxe-vulnerabilities-in-net-core/