diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b7db7d..a802277 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 --- develop ---
 
+* security: Escape threshold web output and harden RLIKE filters
 * issue#686: Applying a templated threshold to a graph via the wrench icon, creates a duplicate graph
 * issue#707: Excessive timeout for row caching prevents data from being updated timely
 * issue#710: Fixing Typo in thold_daemons.service File
diff --git a/tests/Unit/TholdRlikeClauseTest.php b/tests/Unit/TholdRlikeClauseTest.php
new file mode 100644
index 0000000..19e5f70
--- /dev/null
+++ b/tests/Unit/TholdRlikeClauseTest.php
@@ -0,0 +1,45 @@
+<?php
+/*
+ +-------------------------------------------------------------------------+
+ | Copyright (C) 2004-2026 The Cacti Group                                 |
+ |                                                                         |
+ | This program is free software; you can redistribute it and/or           |
+ | modify it under the terms of the GNU General Public License             |
+ | as published by the Free Software Foundation; either version 2          |
+ | of the License, or (at your option) any later version.                  |
+ +-------------------------------------------------------------------------+
+ | Cacti: The Complete RRDtool-based Graphing Solution                     |
+ +-------------------------------------------------------------------------+
+ | http://www.cacti.net/                                                   |
+ +-------------------------------------------------------------------------+
+*/
+
+final class TholdRlikeClauseTest extends TestCase {
+	/**
+	 * @return void
+	 */
+	public static function setUpBeforeClass(): void {
+		self::loadPluginSource('thold_functions.php');
+	}
+
+	/**
+	 * @return void
+	 */
+	public function testEmitsTheOperatorAndAQuotedOperand(): void {
+		$this->assertSame("RLIKE 'router'", thold_rlike_clause('router'));
+	}
+
+	/**
+	 * @return void
+	 */
+	public function testQuotesInTheFilterAreEscaped(): void {
+		$this->assertSame("RLIKE ''' OR 1=1 -- '", thold_rlike_clause("' OR 1=1 -- "));
+	}
+
+	/**
+	 * @return void
+	 */
+	public function testCoreHelperIsPreferredWhenAvailable(): void {
+		$this->assertSame(db_qstr_rlike('x'), thold_rlike_clause('x'));
+	}
+}
diff --git a/thold.php b/thold.php
index 0bf86f4..e9c491c 100644
--- a/thold.php
+++ b/thold.php
@@ -614,7 +614,7 @@ function list_tholds() {
 	}
 
 	if (get_request_var('rfilter') != '') {
-		$sql_where .= ($sql_where == '' ? '(' : ' AND ') . " td.name_cache RLIKE '" . get_request_var('rfilter') . "'";
+		$sql_where .= ($sql_where == '' ? '(' : ' AND ') . ' td.name_cache ' . thold_rlike_clause(get_request_var('rfilter'));
 	}
 
 	if ($statefilter != '') {
@@ -763,18 +763,18 @@ function list_tholds() {
 				</tr>
 			</table>
 			<input type='hidden' name='search' value='search'>
-			<input type='hidden' id='page' value='<?php print get_filter_request_var('page'); ?>'>
+			<input type='hidden' id='page' value='<?php print html_escape(get_filter_request_var('page')); ?>'>
 		</form>
 		<script type='text/javascript'>
 
 		function applyFilter() {
 			strURL  = 'thold.php?header=false&host_id=' + $('#host_id').val();
-			strURL += '&state=' + $('#state').val();
-			strURL += '&thold_template_id=' + $('#thold_template_id').val();
-			strURL += '&data_template_id=' + $('#data_template_id').val();
-			strURL += '&site_id=' + $('#site_id').val();
-			strURL += '&rows=' + $('#rows').val();
-			strURL += '&rfilter=' + base64_encode($('#rfilter').val());
+			strURL += '&state=' + encodeURIComponent($('#state').val());
+			strURL += '&thold_template_id=' + encodeURIComponent($('#thold_template_id').val());
+			strURL += '&data_template_id=' + encodeURIComponent($('#data_template_id').val());
+			strURL += '&site_id=' + encodeURIComponent($('#site_id').val());
+			strURL += '&rows=' + encodeURIComponent($('#rows').val());
+			strURL += '&rfilter=' + encodeURIComponent(base64_encode($('#rfilter').val()));
 			loadPageNoHeader(strURL);
 		}
 
diff --git a/thold_functions.php b/thold_functions.php
index fa3c270..b4448ad 100644
--- a/thold_functions.php
+++ b/thold_functions.php
@@ -8401,6 +8401,22 @@ function thold_get_cached_name(&$thold_data) {
 	return $thold_data['name_cache'];
 }
 
+/**
+ * Quote a value for an RLIKE comparison using the hardened core helper when
+ * available while retaining compatibility with older supported Cacti builds.
+ *
+ * @param string $value Raw filter value.
+ *
+ * @return string RLIKE operator and quoted operand.
+ */
+function thold_rlike_clause($value) {
+	if (function_exists('db_qstr_rlike')) {
+		return db_qstr_rlike($value);
+	}
+
+	return 'RLIKE ' . db_qstr($value);
+}
+
 /**
  * Substitute one tag, rendering an absent value as an empty string.
  *
diff --git a/thold_graph.php b/thold_graph.php
index 619f2ee..7765293 100644
--- a/thold_graph.php
+++ b/thold_graph.php
@@ -251,20 +251,20 @@ function form_thold_filter() {
 					</td>
 				</tr>
 			</table>
-			<input type='hidden' id='page' value='<?php print get_request_var('page'); ?>'>
+			<input type='hidden' id='page' value='<?php print html_escape(get_request_var('page')); ?>'>
 			<input type='hidden' id='tab' value='thold'>
 		</form>
 		<script type='text/javascript'>
 
 		function applyFilter() {
 			strURL  = 'thold_graph.php?header=false&action=thold';
-			strURL += '&state=' + $('#state').val();
-			strURL += '&thold_template_id=' + $('#thold_template_id').val();
-			strURL += '&data_template_id=' + $('#data_template_id').val();
-			strURL += '&host_id=' + $('#host_id').val();
-			strURL += '&site_id=' + $('#site_id').val();
-			strURL += '&rows=' + $('#rows').val();
-			strURL += '&rfilter=' + base64_encode($('#rfilter').val());
+			strURL += '&state=' + encodeURIComponent($('#state').val());
+			strURL += '&thold_template_id=' + encodeURIComponent($('#thold_template_id').val());
+			strURL += '&data_template_id=' + encodeURIComponent($('#data_template_id').val());
+			strURL += '&host_id=' + encodeURIComponent($('#host_id').val());
+			strURL += '&site_id=' + encodeURIComponent($('#site_id').val());
+			strURL += '&rows=' + encodeURIComponent($('#rows').val());
+			strURL += '&rfilter=' + encodeURIComponent(base64_encode($('#rfilter').val()));
 			loadPageNoHeader(strURL);
 		}
 
@@ -404,7 +404,7 @@ function tholds() {
 	$statefilter = thold_get_state_filter(get_request_var('state'));
 
 	if (get_request_var('rfilter') != '') {
-		$sql_where .= ($sql_where == '' ? '(' : ' AND ') . " td.name_cache RLIKE '" . get_request_var('rfilter') . "'";
+		$sql_where .= ($sql_where == '' ? '(' : ' AND ') . 'td.name_cache ' . thold_rlike_clause(get_request_var('rfilter'));
 	}
 
 	if (get_request_var('data_template_id') != '-1') {
@@ -937,8 +937,8 @@ function hosts() {
 
 	if (get_request_var('rfilter') != '') {
 		$sql_where .= " (h.deleted = ''
-			AND (h.hostname RLIKE '" . get_request_var('rfilter') . "'
-			OR h.description RLIKE '" . get_request_var('rfilter') . "')";
+			AND (h.hostname " . thold_rlike_clause(get_request_var('rfilter')) . '
+			OR h.description ' . thold_rlike_clause(get_request_var('rfilter')) . ')';
 	}
 
 	if (get_request_var('host_status') == '-1') {
@@ -1261,18 +1261,18 @@ function form_host_filter() {
 					</td>
 				</tr>
 			</table>
-			<input type='hidden' name='page' value='<?php print get_request_var('page'); ?>'>
+			<input type='hidden' name='page' value='<?php print html_escape(get_request_var('page')); ?>'>
 			<input type='hidden' name='tab' value='hoststat'>
 		</form>
 		<script type='text/javascript'>
 
 		function applyFilter() {
 			strURL  = 'thold_graph.php?header=false&action=hoststat';
-			strURL += '&host_status=' + $('#host_status').val();
-			strURL += '&host_template_id=' + $('#host_template_id').val();
-			strURL += '&site_id=' + $('#site_id').val();
-			strURL += '&rows=' + $('#rows').val();
-			strURL += '&rfilter=' + base64_encode($('#rfilter').val());
+			strURL += '&host_status=' + encodeURIComponent($('#host_status').val());
+			strURL += '&host_template_id=' + encodeURIComponent($('#host_template_id').val());
+			strURL += '&site_id=' + encodeURIComponent($('#site_id').val());
+			strURL += '&rows=' + encodeURIComponent($('#rows').val());
+			strURL += '&rfilter=' + encodeURIComponent(base64_encode($('#rfilter').val()));
 			loadPageNoHeader(strURL);
 		}
 
@@ -1395,7 +1395,7 @@ function thold_export_log() {
 	}
 
 	if (get_request_var('rfilter') != '') {
-		$sql_where .= ($sql_where == '' ? '' : ' AND') . " tl.description RLIKE '" . get_request_var('rfilter') . "'";
+		$sql_where .= ($sql_where == '' ? '' : ' AND') . ' tl.description ' . thold_rlike_clause(get_request_var('rfilter'));
 	}
 
 	$sql_order  = '';
@@ -1490,7 +1490,7 @@ function thold_show_log() {
 	}
 
 	if (get_request_var('rfilter') != '') {
-		$sql_where .= ($sql_where == '' ? '' : ' AND') . " tl.description RLIKE '" . get_request_var('rfilter') . "'";
+		$sql_where .= ($sql_where == '' ? '' : ' AND') . ' tl.description ' . thold_rlike_clause(get_request_var('rfilter'));
 	}
 
 	$sql_order = get_order_string();
@@ -1734,13 +1734,13 @@ function form_thold_log_filter() {
 
 		function applyFilter() {
 			strURL  = 'thold_graph.php?header=false&action=log';
-			strURL += '&status=' + $('#status').val();
-			strURL += '&threshold_id=' + $('#threshold_id').val();
-			strURL += '&thold_template_id=' + $('#thold_template_id').val();
-			strURL += '&host_id=' + $('#host_id').val();
-			strURL += '&site_id=' + $('#site_id').val();
-			strURL += '&rows=' + $('#rows').val();
-			strURL += '&rfilter=' + base64_encode($('#rfilter').val());
+			strURL += '&status=' + encodeURIComponent($('#status').val());
+			strURL += '&threshold_id=' + encodeURIComponent($('#threshold_id').val());
+			strURL += '&thold_template_id=' + encodeURIComponent($('#thold_template_id').val());
+			strURL += '&host_id=' + encodeURIComponent($('#host_id').val());
+			strURL += '&site_id=' + encodeURIComponent($('#site_id').val());
+			strURL += '&rows=' + encodeURIComponent($('#rows').val());
+			strURL += '&rfilter=' + encodeURIComponent(base64_encode($('#rfilter').val()));
 			loadPageNoHeader(strURL);
 		}
 
@@ -1751,13 +1751,13 @@ function clearFilter() {
 
 		function exportLog() {
 			strURL  = 'thold_graph.php?action=exportlog';
-			strURL += '&status=' + $('#status').val();
-			strURL += '&threshold_id=' + $('#threshold_id').val();
-			strURL += '&thold_template_id=' + $('#thold_template_id').val();
-			strURL += '&host_id=' + $('#host_id').val();
-			strURL += '&site_id=' + $('#site_id').val();
-			strURL += '&rows=' + $('#rows').val();
-			strURL += '&rfilter=' + base64_encode($('#rfilter').val());
+			strURL += '&status=' + encodeURIComponent($('#status').val());
+			strURL += '&threshold_id=' + encodeURIComponent($('#threshold_id').val());
+			strURL += '&thold_template_id=' + encodeURIComponent($('#thold_template_id').val());
+			strURL += '&host_id=' + encodeURIComponent($('#host_id').val());
+			strURL += '&site_id=' + encodeURIComponent($('#site_id').val());
+			strURL += '&rows=' + encodeURIComponent($('#rows').val());
+			strURL += '&rfilter=' + encodeURIComponent(base64_encode($('#rfilter').val()));
 			document.location = strURL;
 			Pace.stop();
 		}
diff --git a/thold_templates.php b/thold_templates.php
index ea379ef..3dd7db9 100644
--- a/thold_templates.php
+++ b/thold_templates.php
@@ -2186,7 +2186,7 @@ function templates() {
 
 			function applyFilter() {
 				strURL  = 'thold_templates.php?header=false&rows=' + $('#rows').val();
-				strURL += '&filter=' + $('#filter').val();
+				strURL += '&filter=' + encodeURIComponent($('#filter').val());
 				loadPageNoHeader(strURL);
 			}
 
diff --git a/thold_webapi.php b/thold_webapi.php
index 25ff3b9..c96ebbd 100644
--- a/thold_webapi.php
+++ b/thold_webapi.php
@@ -793,39 +793,39 @@ function thold_wizard() {
 
 	function applyTholdFilter() {
 		strURL  = 'thold.php?action=add&header=false';
-		strURL += '&type_id=' + $('#type_id').val();
+		strURL += '&type_id=' + encodeURIComponent($('#type_id').val());
 
 		if ($('#type_id').val() == 'thold') {
 			if ($('#my_host_id').length && $('#my_host_id').val() > 0) {
-				strURL += '&my_host_id=' + $('#my_host_id').val();
+				strURL += '&my_host_id=' + encodeURIComponent($('#my_host_id').val());
 			}
 
 			if ($('#local_graph_id').length && $('#local_graph_id').val() > 0) {
-				strURL += '&local_graph_id=' + $('#local_graph_id').val();
+				strURL += '&local_graph_id=' + encodeURIComponent($('#local_graph_id').val());
 			}
 
 			if ($('#data_template_rrd_id').length && $('#data_template_rrd_id').val() > 0) {
-				strURL += '&data_template_rrd_id=' + $('#data_template_rrd_id').val();
+				strURL += '&data_template_rrd_id=' + encodeURIComponent($('#data_template_rrd_id').val());
 			}
 		} else {
 			if ($('#thold_template_id').length && $('#thold_template_id').val() > 0) {
-				strURL += '&thold_template_id=' + $('#thold_template_id').val();
+				strURL += '&thold_template_id=' + encodeURIComponent($('#thold_template_id').val());
 			}
 
 			if ($('#graph_template_id').length && $('#graph_template_id').val() > 0) {
-				strURL += '&graph_template_id=' + $('#graph_template_id').val();
+				strURL += '&graph_template_id=' + encodeURIComponent($('#graph_template_id').val());
 			}
 
 			if ($('#data_query_id').length && $('#data_query_id').val() > 0) {
-				strURL += '&data_query_id=' + $('#data_query_id').val();
+				strURL += '&data_query_id=' + encodeURIComponent($('#data_query_id').val());
 			}
 
 			if ($('#data_template_id').length && $('#data_template_id').val() > 0) {
-				strURL += '&data_template_id=' + $('#data_template_id').val();
+				strURL += '&data_template_id=' + encodeURIComponent($('#data_template_id').val());
 			}
 
 			if ($('#my_host_id').length && $('#my_host_id').val() != 0) {
-				strURL += '&my_host_id=' + $('#my_host_id').val();
+				strURL += '&my_host_id=' + encodeURIComponent($('#my_host_id').val());
 			}
 
 			if ($('#snmp_index').length && $('#snmp_index').val() != '') {
@@ -861,7 +861,37 @@ function applyTholdFilter() {
 function thold_new_graphs_save($host_id) {
 	$return_array = false;
 
-	$selected_graphs_array = cacti_unserialize(stripslashes(get_nfilter_request_var('selected_graphs_array')));
+	// Nested wizard structure (cg/sg), not a flat ID list. Flat
+	// sanitize_unserialize_selected_items() rejects nested arrays and would
+	// break graph creation. Prefer the graphs-specific sanitizer when present
+	// (Cacti develop+); otherwise unserialize with allowed_classes => false.
+	$raw = get_nfilter_request_var('selected_graphs_array');
+
+	if (function_exists('sanitize_unserialize_selected_graphs')) {
+		$selected_graphs_array = sanitize_unserialize_selected_graphs($raw);
+	} elseif (function_exists('cacti_unserialize') && is_string($raw) && $raw !== '') {
+		$selected_graphs_array = cacti_unserialize(stripslashes($raw));
+	} elseif (is_string($raw) && $raw !== '') {
+		$unstripped = stripslashes($raw);
+
+		if (preg_match('/^a:[0-9]+:{/', $unstripped) && !preg_match('/(^|;|{|})O:\+?[0-9]+:"/', $unstripped)) {
+			$selected_graphs_array = unserialize($unstripped, ['allowed_classes' => false]);
+		} else {
+			$selected_graphs_array = false;
+		}
+	} else {
+		$selected_graphs_array = false;
+	}
+
+	if (!is_array($selected_graphs_array)) {
+		return false;
+	}
+
+	foreach ($selected_graphs_array as $form_type => $form_array) {
+		if (($form_type !== 'cg' && $form_type !== 'sg') || !is_array($form_array)) {
+			return false;
+		}
+	}
 
 	$values = [];