From 8966d851bef4a0406bd55835f3bf5cd6ba0a6aec Mon Sep 17 00:00:00 2001
From: "Gregory P. Smith" <greg@krypto.org>
Date: Sun, 5 Apr 2026 10:40:33 -0700
Subject: [PATCH] gh-94632: document the subprocess need for extra_groups=()
 with user=

---
 Doc/library/subprocess.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 9e261a0ca03902..fe64daa3291d67 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -627,6 +627,12 @@ functions.
    the value in ``pw_uid`` will be used. If the value is an integer, it will
    be passed verbatim. (POSIX only)
 
+   .. note::
+
+      Specifying *user* will not drop existing supplementary group memberships!
+      The caller must also pass ``extra_groups=()`` to reduce the group membership
+      of the child process for security purposes.
+
    .. availability:: POSIX
    .. versionadded:: 3.9