Updates release notes for PR #4490

.release-notes/next-release.md

@@ -8,3 +8,27 @@ Back in August of 2023, we had to drop MacOS on Apple Silicon as a supported pla
 
 GitHub recently announced that they now have Apple Silicon MacOS machines so, we are back in business and MacOS on Apple Silicon is once again a supported platform.
 
+## Fix for potential memory corruption in `Array.copy_to`
+
+`Array.copy_to` did not check whether the source or destination Arrays had been initialized or whether the requested number of elements to be copied exceeded the number of available elements (allocated memory). These issues would result in potential dereferencing of a null pointer or attempts to access unallocated memory.
+
+Before this fix, the following code would print `11` then `0`:
+
+```pony
+actor Main
+  new create(e: Env) =>
+    var src: Array[U8] = [1]
+    var dest: Array[U8] = [11; 1; 2; 3; 4; 5; 6]
+
+    try
+      e.out.print(dest(0)?.string())
+    end
+    src.copy_to(dest, 11, 0, 10)
+
+    try
+      e.out.print(dest(0)?.string())
+    end
+```
+
+After the fix, this code correctly prints `11` and `11`.
+