diff --git a/ChangeLog b/ChangeLog
index ea3c35700d..1efd3dd419 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Aug 27 19:10:50 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* ext/etc/etc.c (etc_getlogin): update documentation to note
+	  security issue.  [ruby-Bugs-11821]
+
 Mon Aug 27 15:56:48 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* string.c (sym_encoding): return the encoding of a Symbol.
diff --git a/ext/etc/etc.c b/ext/etc/etc.c
index 94c8b6b85f..7c8fba3b8f 100644
--- a/ext/etc/etc.c
+++ b/ext/etc/etc.c
@@ -35,6 +35,8 @@ char *getenv();
 char *getlogin();
 
 /* Returns the short user name of the currently logged in user.
+ * Unfortunately, it is often rather easy to fool getlogin().
+ * Avoid getlogin() for security-related purposes.
  *
  * e.g.
  *   Etc.getlogin -> 'guest'