diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
index b735e9c..d1e5045 100644
--- a/Doc/whatsnew/3.6.rst
+++ b/Doc/whatsnew/3.6.rst
@@ -141,16 +141,25 @@
 =============
 
 * The ASCII decoder is now up to 60 times as fast for error handlers:
-  ``surrogateescape``, ``ignore`` and ``replace``.
+  ``surrogateescape``, ``ignore`` and ``replace`` (Contributed
+  by Victor Stinner in :issue:`24870`).
 
 * The ASCII and the Latin1 encoders are now up to 3 times as fast for the error
-  error ``surrogateescape``.
+  error ``surrogateescape`` (Contributed by Victor Stinner in :issue:`25227`).
 
 * The UTF-8 encoder is now up to 75 times as fast for error handlers:
-  ``ignore``, ``replace``, ``surrogateescape``, ``surrogatepass``.
+  ``ignore``, ``replace``, ``surrogateescape``, ``surrogatepass`` (Contributed
+  by Victor Stinner in :issue:`25267`).
 
 * The UTF-8 decoder is now up to 15 times as fast for error handlers:
-  ``ignore``, ``replace`` and ``surrogateescape``.
+  ``ignore``, ``replace`` and ``surrogateescape`` (Contributed
+  by Victor Stinner in :issue:`25301`).
+
+* ``bytes % args`` is now up to 2 times faster. (Contributed by Victor Stinner
+  in :issue:`25349`).
+
+* ``bytearray % args`` is now between 2.5 and 5 times faster. (Contributed by
+  Victor Stinner in :issue:`25399`).
 
 
 Build and C API Changes
diff --git a/Misc/NEWS b/Misc/NEWS
index 2700ad3..97e5e77 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #25399: Optimize bytearray % args using the new private _PyBytesWriter
+  API. Formatting is now between 2.5 and 5 times faster.
+
 - Issue #25274: sys.setrecursionlimit() now raises a RecursionError if the new
   recursion limit is too low depending at the current recursion depth. Modify
   also the "lower-water mark" formula to make it monotonic. This mark is used
@@ -19,6 +22,7 @@
   sys.stdout.fileno() fails.
 
 - Issue #25349: Optimize bytes % args using the new private _PyBytesWriter API.
+  Formatting is now up to 2 times faster.
 
 - Issue #24806: Prevent builtin types that are not allowed to be subclassed from
   being subclassed through multiple inheritance.