diff --git a/main/admin/settings.lib.php b/main/admin/settings.lib.php
index 2ccadc835e..3a5a841aa7 100755
--- a/main/admin/settings.lib.php
+++ b/main/admin/settings.lib.php
@@ -758,7 +758,7 @@ function handle_search()
         $group = array();
         $url =  Display::div(Display::url(get_lang('AddSpecificSearchField'), 'specific_fields.php'), array('class'=>'sectioncomment'));
         if (empty($sf_values)) {
-            $form->addElement('html', get_lang('SearchPrefilterPrefix').$url);
+            $form->addElement('label', [get_lang('SearchPrefilterPrefix'), $url]);
         } else {
             $form->addElement('select', 'search_prefilter_prefix', array(get_lang('SearchPrefilterPrefix'), $url), $sf_values, '');
             $default_values['search_prefilter_prefix'] = api_get_setting('search_prefilter_prefix');
@@ -839,8 +839,14 @@ function handle_search()
             $list_of_programs = array('pdftotext','ps2pdf', 'catdoc','html2text','unrtf', 'catppt', 'xls2csv');
 
             foreach($list_of_programs as $program) {
-                $output = $ret_val = null;
+                $output = [];
+                $ret_val = null;
                 exec("which $program", $output, $ret_val);
+
+                if (!$output) {
+                    $output[] = '';
+                }
+
                 $icon = Display::return_icon('bullet_red.png', get_lang('NotInstalled'));
                 if (!empty($output[0])) {
                     $icon = Display::return_icon('bullet_green.png', get_lang('Installed'));
diff --git a/main/admin/specific_fields.php b/main/admin/specific_fields.php
index b8f0a1096f..d3684df331 100755
--- a/main/admin/specific_fields.php
+++ b/main/admin/specific_fields.php
@@ -17,7 +17,6 @@ api_protect_admin_script();
 // Breadcrumb
 $interbreadcrumb[] = array ('url' => 'index.php', 'name' => get_lang('PlatformAdmin'));
 $interbreadcrumb[] = array ('url' => 'settings.php?category=Search', 'name' => get_lang('PlatformConfigSettings'));
-$interbreadcrumb[] = array ('url' => 'specific_fields.php', 'name' => get_lang('SpecificSearchFields'));
 
 $libpath = api_get_path(LIBRARY_PATH);
 
@@ -30,16 +29,16 @@ $renderer->setCustomElementTemplate('<span>{element}</span> ');
 $form->addElement('static','search_advanced_link',null,'<a href="specific_fields_add.php">'.Display::return_icon('fieldadd.gif').get_lang('AddSpecificSearchField').'</a>');
 
 // Create a sortable table with specific fields data
-$column_show = array(1,1,1,1);
-$column_order = array(3,2,1,4);
+$column_show = array(1,1,1);
+$column_order = array(3,2,1);
 $extra_fields = get_specific_field_list();
 $number_of_extra_fields = count($extra_fields);
 
 $table = new SortableTableFromArrayConfig($extra_fields,2,50,'',$column_show,$column_order);
-$table->set_header(0, '', false,null,'width="2%"', 'style="display:none"');
+$table->set_header(0, '&nbsp;', false,null,'width="2%"', 'style="display:none"');
 $table->set_header(1, get_lang('Code'), TRUE, 'width="10%"');
 $table->set_header(2, get_lang('Name'));
-$table->set_header(3, get_lang('Modify'),true,'width="10%"');
+$table->set_header(3, get_lang('Modify'),false,'width="10%"');
 $table->set_column_filter(3, 'edit_filter');
 
 function edit_filter($id,$url_params,$row) {
@@ -49,15 +48,16 @@ function edit_filter($id,$url_params,$row) {
 	return $return;
 }
 
-if ($_REQUEST['action'] == 'delete') {
+if (isset($_REQUEST['action']) && $_REQUEST['action'] == 'delete') {
 	delete_specific_field($_REQUEST['field_id']);
 	header('Location: specific_fields.php?message='.get_lang('FieldRemoved'));
+    exit;
 }
 
 // Start output
 
 // Displaying the header
-Display::display_header($nameTools);
+Display::display_header(get_lang('SpecificSearchFields'));
 echo Display::display_normal_message(get_lang('SpecificSearchFieldsIntro'));
 
 if(!empty($_GET['message'])) {
diff --git a/main/admin/specific_fields_add.php b/main/admin/specific_fields_add.php
index 232ab2a996..9d394159cb 100755
--- a/main/admin/specific_fields_add.php
+++ b/main/admin/specific_fields_add.php
@@ -18,18 +18,21 @@ $this_section = SECTION_PLATFORM_ADMIN;
 // user permissions
 api_protect_admin_script();
 
+$fieldId = isset($_REQUEST['field_id']) ? intval($_REQUEST['field_id']) : 0;
+
 $interbreadcrumb[] = array('url' => 'index.php', 'name' => get_lang('PlatformAdmin'));
 $interbreadcrumb[] = array('url' => 'settings.php?category=Search', 'name' => get_lang('PlatformConfigSettings'));
 $interbreadcrumb[] = array('url' => 'specific_fields.php', 'name' => get_lang('SpecificSearchFields'));
-if ($_GET['action']<>'edit') {
-  $tool_name = get_lang('AddSpecificSearchField');
-} else {
+
+$tool_name = get_lang('AddSpecificSearchField');
+
+if (isset($_GET['action']) && $_GET['action'] === 'edit') {
   $tool_name = get_lang('EditSpecificSearchField');
 }
 // Create the form
 $form = new FormValidator('specific_fields_add');
 // Field variable name
-$form->addElement('hidden','field_id',(int)$_REQUEST['field_id']);
+$form->addElement('hidden','field_id', $fieldId);
 $form->addElement('text','field_name',get_lang('FieldName'));
 $form->applyFilter('field_name','html_filter');
 $form->applyFilter('field_name','trim');
@@ -39,8 +42,8 @@ $form->addRule('field_name', '', 'maxlength',20);
 
 // Set default values (only not empty when editing)
 $defaults = array();
-if (is_numeric($_REQUEST['field_id'])) {
-    $form_information = get_specific_field_list(array( 'id' => (int)$_GET['field_id'] ));
+if ($fieldId) {
+    $form_information = get_specific_field_list(array( 'id' => $fieldId ));
     $defaults['field_name'] = $form_information[0]['name'];
 }
 $form->setDefaults($defaults);
diff --git a/main/document/upload.php b/main/document/upload.php
index a2e307fa05..f7fb1b9d01 100755
--- a/main/document/upload.php
+++ b/main/document/upload.php
@@ -258,11 +258,11 @@ if (api_get_setting('search_enabled') == 'true') {
     $form->addElement('checkbox', 'index_document', '', get_lang('SearchFeatureDoIndexDocument').'<div style="font-size: 80%" >'.$supported_formats.'</div>');
     $form->addElement('html', '<br /><div class="sub-form">');
     $form->addElement('html', '<div class="label">'.get_lang('SearchFeatureDocumentLanguage').'</div>');
-    $form->addElement('html', '<div>' . api_get_languages_combo(null) . '</div>');
+    $form->addLabel(get_lang('Language'), api_get_languages_combo());
     $form->addElement('html', '</div><div class="sub-form">');
     $specific_fields = get_specific_field_list();
     foreach ($specific_fields as $specific_field) {
-        $form->addElement('text', $specific_field['code'], $specific_field['name'].' : ');
+        $form->addElement('text', $specific_field['code'], $specific_field['name']);
     }
     $form->addElement('html', '</div>');
 }
diff --git a/main/exercice/exercise.class.php b/main/exercice/exercise.class.php
index d67d1d8c23..fa4f949fa2 100755
--- a/main/exercice/exercise.class.php
+++ b/main/exercice/exercise.class.php
@@ -1315,7 +1315,12 @@ class Exercise
 
                 foreach ($specific_fields as $specific_field) {
                     $form->addElement ('text', $specific_field['code'], $specific_field['name']);
-                    $filter = array('c_id'=> "'". api_get_course_int_id() ."'", 'field_id' => $specific_field['id'], 'ref_id' => $this->id, 'tool_id' => '\''. TOOL_QUIZ .'\'');
+                    $filter = array(
+                        'c_id' => api_get_course_int_id(),
+                        'field_id' => $specific_field['id'],
+                        'ref_id' => $this->id,
+                        'tool_id' => "'" . TOOL_QUIZ . "'"
+                    );
                     $values = get_specific_field_values_list($filter, array('value'));
                     if ( !empty($values) ) {
                         $arr_str_values = array();
diff --git a/main/inc/lib/api.lib.php b/main/inc/lib/api.lib.php
index 24a7de5c8b..6479309d9c 100644
--- a/main/inc/lib/api.lib.php
+++ b/main/inc/lib/api.lib.php
@@ -4179,7 +4179,7 @@ function api_get_languages_combo($name = 'language')
     $languages  = $language_list['name'];
     $folder     = $language_list['folder'];
 
-    $ret .= '<select name="' . $name . '" id="language_chosen">';
+    $ret .= '<select name="' . $name . '" id="language_chosen" class="selectpicker show-tick form-control">';
     foreach ($languages as $key => $value) {
         if ($folder[$key] == $default) {
             $selected = ' selected="selected"';
diff --git a/main/inc/lib/search/search_widget.php b/main/inc/lib/search/search_widget.php
index aa49c0f0ec..5d569e0304 100755
--- a/main/inc/lib/search/search_widget.php
+++ b/main/inc/lib/search/search_widget.php
@@ -67,7 +67,7 @@ function format_specific_fields_selects($sf_terms, $op, $prefilter_prefix='') {
     // Process each prefix type term
     $i = 0;
     $max = count($sf_terms);
-    $multiple_selects .='';
+    $multiple_selects ='';
     foreach ($sf_terms as $prefix => $sf_term_array) {
         if ($prefix == $prefilter_prefix) continue;
         $multiple_select = '';
@@ -91,7 +91,7 @@ function format_specific_fields_selects($sf_terms, $op, $prefilter_prefix='') {
         // get specific field name
         $sf_value = get_specific_field_list(array( 'code' => "'$prefix'" ));
         $sf_value = array_shift($sf_value);
-        $multiple_select .= '<td><label class="sf-select-multiple-title" for="sf_'. $prefix .'[]">'.$icons_for_search_terms[$prefix].' '.$sf_value['name'].'</label><br />';
+        $multiple_select .= '<td><label class="sf-select-multiple-title" for="sf_'. $prefix .'[]">' . $sf_value['name'].'</label><br />';
         $multiple_select .= format_one_specific_field_select($prefix, $sf_term_array, $op, 'multiple="multiple" size="7" class="sf-select-multiple"');
         $multiple_select .= '</td>';
         $multiple_selects .= $multiple_select;
@@ -134,8 +134,10 @@ function search_widget_normal_form($action, $show_thesaurus, $sf_terms, $op) {
         $reset_button 	= '<button class="save"   type="submit" id="tags-clean" value="'. get_lang('SearchResetKeywords') .'" />'. get_lang('SearchResetKeywords') .'</button> ';
 	}
 
+    $query = isset($_REQUEST['query']) ? Security::remove_XSS($_REQUEST['query']) : null;
+
     $form = '<form id="chamilo_search" action="'. $action .'" method="GET">
-            <input type="text" id="query" name="query" size="40" value="'.stripslashes(Security::remove_XSS($_REQUEST['query'])).'" />
+            <input type="text" id="query" name="query" size="40" value="' . $query . '" />
             <input type="hidden" name="mode" value="'. $mode .'"/>
             <input type="hidden" name="type" value="'. $type .'"/>
             <input type="hidden" name="tablename_page_nr" value="1" />
@@ -357,7 +359,7 @@ function search_widget_show($action='index.php')
     //check if URL params are defined (to see if we show the thesaurus or not)
     $show_thesaurus = false;
     foreach ($url_params as $param) {
-        if (is_array($_REQUEST[$param])) {
+        if (isset($_REQUEST[$param]) && is_array($_REQUEST[$param])) {
             $thesaurus_decided = FALSE;
             foreach ($_REQUEST[$param] as $term) {
                 if (!empty($term)) {
diff --git a/main/newscorm/lp_list_search.php b/main/newscorm/lp_list_search.php
index 4783464d37..54bca35dac 100755
--- a/main/newscorm/lp_list_search.php
+++ b/main/newscorm/lp_list_search.php
@@ -49,10 +49,14 @@ if (!empty($_REQUEST['operator']) && in_array($op, array('or', 'and'))) {
     $op = $_REQUEST['operator'];
 }
 
-$query = stripslashes(htmlspecialchars_decode($_REQUEST['query'], ENT_QUOTES));
+$query = null;
+
+if (isset($_REQUEST['query'])) {
+    $query = stripslashes(htmlspecialchars_decode($_REQUEST['query'], ENT_QUOTES));
+}
 
 $mode = 'default';
-if (in_array($_GET['mode'], array('gallery', 'default'))) {
+if (isset($_GET['mode']) && in_array($_GET['mode'], array('gallery', 'default'))) {
     $mode = $_GET['mode'];
 }
 
@@ -111,12 +115,17 @@ if (count($term_array)) {
     }
 }
 
-list($count, $results) = chamilo_query_query(
-    api_convert_encoding($query, 'UTF-8', $charset),
-    0,
-    1000,
-    $fixed_queries
-);
+if ($query) {
+    list($count, $results) = chamilo_query_query(
+        api_convert_encoding($query, 'UTF-8', $charset),
+        0,
+        1000,
+        $fixed_queries
+    );
+} else {
+    $count = 0;
+    $results = [];
+}
 
 // Prepare blocks to show.
 $blocks = array();