API / CoW: Copy NumPy arrays by default in DataFrame constructor

doc/source/whatsnew/v2.0.0.rst

@@ -190,6 +190,10 @@ Copy-on-Write improvements
   of Series objects and specifying ``copy=False``, will now use a lazy copy
   of those Series objects for the columns of the DataFrame (:issue:`50777`)
 
+- The :class:`DataFrame` constructor, when constructing from a NumPy array,
+  will now copy the array by default to avoid mutating the :class:`DataFrame`
+  when mutating the array. Specify ``copy=False`` to get the old behavior.
+
 - Trying to set values using chained assignment (for example, ``df["a"][1:3] = 0``)
   will now always raise an warning when Copy-on-Write is enabled. In this mode,
   chained assignment can never work because we are always setting into a temporary