diff --git a/README.md b/README.md
index 4875694..6a5bf39 100644
--- a/README.md
+++ b/README.md
@@ -6,3 +6,9 @@ This project demonstrates how to run Kestrel without ASP.NET.  It creates a web
 It also demonstrates how to add the websocket middleware.  If you connect to ws://localhost:8080 (with wscat, for example) it will again respond with "hello world".  This time it will be sent as a textual websocket message.
 
 I wrote this code because I was curious to see if it could be done, but it may be interesting for someone.  It uses significantly less memory than ASP.NET.
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+---
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+In July 2022, GitHub notified me of vulnerabilities in this repository's dependencies.  I accepted their automated patches, but I no longer have .NET Core 2.1 installed, so it's difficult to test the result.  Hopefully it will still work, but you may encounter difficulties.
+
+.NET Core 2.1 reached end of life in August 2021.  Because of this, you should not expect to be able to create secure applications based on this repository.