libxslt: minor update to fix DOS security problem

pkgs/development/libraries/libxslt/default.nix

@@ -1,11 +1,11 @@
 { stdenv, fetchurl, libxml2 }:
 
 stdenv.mkDerivation (rec {
-  name = "libxslt-1.1.27";
+  name = "libxslt-1.1.28";
 
   src = fetchurl {
     url = "ftp://xmlsoft.org/libxml2/${name}.tar.gz";
-    sha256 = "09ky3vhlaahvsb0q9gp6h3as53pfj70gincirachjqzj46jdka5n";
+    sha256 = "13029baw9kkyjgr7q3jccw2mz38amq7mmpr5p3bh775qawd1bisz";
   };
 
   buildInputs = [ libxml2 ];