From 1edef50880f740e00fa1cd501c2ac56ec6fd10e4 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Wed, 30 Oct 2013 08:11:31 -0400
Subject: [PATCH] Fixed #21316 -- Documented that modifying safe strings makes
 them unsafe.

Thanks dev@simon.net.nz for the suggestion and vijay_shanker for the patch.
---
 docs/ref/utils.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/docs/ref/utils.txt b/docs/ref/utils.txt
index e03a775d60..a1e74b0810 100644
--- a/docs/ref/utils.txt
+++ b/docs/ref/utils.txt
@@ -764,6 +764,17 @@ appropriate entities.
 
     Can be called multiple times on a single string.
 
+    String marked safe will become unsafe again if modified. For example::
+
+        >>> mystr = '<b>Hello World</b>   '
+        >>> mystr = mark_safe(mystr)
+        >>> type(mystr)
+        <class 'django.utils.safestring.SafeBytes'>
+
+        >>> mystr = mystr.strip()  # removing whitespace
+        >>> type(mystr)
+        <type 'str'>
+
 .. function:: mark_for_escaping(s)
 
     Explicitly mark a string as requiring HTML escaping upon output. Has no