Index: moodle/mod/lamslesson/callback.php
===================================================================
diff -u -r4b0e8db9f2b4f097606ba7dda5ea0c6f61094f45 -rc6f6605de18894e645f9a9cabb994996fdf90924
--- moodle/mod/lamslesson/callback.php	(.../callback.php)	(revision 4b0e8db9f2b4f097606ba7dda5ea0c6f61094f45)
+++ moodle/mod/lamslesson/callback.php	(.../callback.php)	(revision c6f6605de18894e645f9a9cabb994996fdf90924)
@@ -18,23 +18,27 @@
 include_once('lib.php');
 global $DB;
 
+$hs = required_param('hs', PARAM_ALPHANUM);
+$ts = required_param('ts', PARAM_RAW);
+$un = required_param('un', PARAM_ALPHANUM);
+$lsid = required_param('lsId', PARAM_INT);
+
 if(!isset($CFG->lamslesson_serverid)||!isset($CFG->lamslesson_serverkey)) {
     header('HTTP/1.1 401 Unauthenticated');
     exit(1);
 }
-$plaintext = trim($_GET['ts']).trim($_GET['un']).trim($CFG->lamslesson_serverid).trim($CFG->lamslesson_serverkey);
+$plaintext = trim($ts).trim($un).trim($CFG->lamslesson_serverid).trim($CFG->lamslesson_serverkey);
 $hash = sha1(strtolower($plaintext));
 
-if($hash!=$_GET['hs']){
+if($hash != $hs){
   header('HTTP/1.1 401 Unauthenticated');
   exit(1);
 }
 
 //OK, the caller is authenticated. Now let's fulfill its request.
 // and make Moodle get the latest marks for this user in this lesson
 
-$lsid = $_GET['lsId'];
-$user = $DB->get_record('user', array('username'=>$_GET['un']));
+$user = $DB->get_record('user', array('username'=>$un));
 if(!$user){
   header('HTTP/1.1 401 Unauthenticated');
   exit(1);
@@ -44,4 +48,4 @@
 
 $gradebookmark = lamslesson_get_lams_outputs($user->username,$lamslesson,$user->username);
 
-?>
\ No newline at end of file
+?>
Index: moodle/mod/lamslesson/lib.php
===================================================================
diff -u -r553eab7725b1f63b96ed6123359c14ad2b2c65e6 -rc6f6605de18894e645f9a9cabb994996fdf90924
--- moodle/mod/lamslesson/lib.php	(.../lib.php)	(revision 553eab7725b1f63b96ed6123359c14ad2b2c65e6)
+++ moodle/mod/lamslesson/lib.php	(.../lib.php)	(revision c6f6605de18894e645f9a9cabb994996fdf90924)
@@ -711,7 +711,7 @@
 		$listofcontexts = '('.$sitecontext->id.')'; // must be site
 	}
 	$sql = "SELECT u.id
-		FROM {$CFG->prefix}user u INNER JOIN {$CFG->prefix}role_assignments r ON u.id=r.userid
+		FROM {user} u INNER JOIN {role_assignments} r ON u.id=r.userid
 		WHERE r.contextid IN $listofcontexts OR r.contextid=$context->id
 		AND u.deleted=0 AND u.username!='guest'";
 	$users = $DB->get_records_sql($sql);
Index: moodle/mod/lamslesson/userinfo.php
===================================================================
diff -u -re4196a23f0ee88b42d53c9e2bcf728170f3da793 -rc6f6605de18894e645f9a9cabb994996fdf90924
--- moodle/mod/lamslesson/userinfo.php	(.../userinfo.php)	(revision e4196a23f0ee88b42d53c9e2bcf728170f3da793)
+++ moodle/mod/lamslesson/userinfo.php	(.../userinfo.php)	(revision c6f6605de18894e645f9a9cabb994996fdf90924)
@@ -16,14 +16,19 @@
     include_once($CFG->libdir.'/datalib.php');
     global $DB;
 
+    $hs = required_param('hs', PARAM_ALPHANUM);
+    $ts = required_param('ts', PARAM_RAW);
+    $un = required_param('un', PARAM_ALPHANUM);
+    $lsid = optional_param('lsid', '', PARAM_INT);
+
     if(!isset($CFG->lamslesson_serverid)||!isset($CFG->lamslesson_serverkey))
     {
         header('HTTP/1.1 401 Unauthenticated');
         exit(1);
     }
-    $plaintext = trim($_GET['ts']).trim($_GET['un']).trim($CFG->lamslesson_serverid).trim($CFG->lamslesson_serverkey);
+    $plaintext = trim($ts).trim($un).trim($CFG->lamslesson_serverid).trim($CFG->lamslesson_serverkey);
     $hash = sha1(strtolower($plaintext));
-    if($hash!=$_GET['hs']){
+    if($hash != $hs){
         header('HTTP/1.1 401 Unauthenticated');
         exit(1);
     }
@@ -32,7 +37,7 @@
     //What it needs is user info in CSV format. It should be like this:
     //username,first name,last name,job title, department, organisation,
     //address,phone,fax,mobile,email
-    $user = $DB->get_record('user', array('username'=>$_GET['un']));
+    $user = $DB->get_record('user', array('username'=>$un));
 
     //return false if none found
     if(!$user){
@@ -43,4 +48,4 @@
     $comma_separated = implode(",", $array);//need more sophiscated algorithm to generate CSV formatted string
     echo $comma_separated;
 
-?>
\ No newline at end of file
+?>