Prevent HTTPoxy attack (CVE-2016-1000110)

Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which
indicates that the script is in CGI mode.

Issue reported and patch contributed by Rémi Rampin.
diff --git a/Misc/ACKS b/Misc/ACKS
index 7aa8fc8..0210a4c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1123,6 +1123,7 @@
 Jeff Ramnani
 Varpu Rantala
 Brodie Rao
+Rémi Rampin
 Senko Rasic
 Antti Rasinen
 Nikolaus Rath
diff --git a/Misc/NEWS b/Misc/NEWS
index 06f10c9..a911bef 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -29,6 +29,10 @@
 Library
 -------
 
+- Issue #27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the
+  HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates
+  that the script is in CGI mode.
+
 - Issue #27130: In the "zlib" module, fix handling of large buffers
   (typically 2 or 4 GiB).  Previously, inputs were limited to 2 GiB, and
   compression and decompression operations did not properly handle results of