Add NEWS item.
diff --git a/Misc/NEWS b/Misc/NEWS
index d6bc73a..5691fd5 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -92,6 +92,8 @@
 Library
 -------
 
+- Issue #5647: MutableSet.__iand__() no longer mutates self during iteration.
+
 - Issue #5619: Multiprocessing children disobey the debug flag and causes
   popups on windows buildbots. Patch applied to work around this issue.