diff --git a/lib/common.lib.php b/lib/common.lib.php
index 5ee99b547..526d36f4f 100644
--- a/lib/common.lib.php
+++ b/lib/common.lib.php
@@ -2881,7 +2881,7 @@ function clean_query_string($query, $amp=true)
         $q = array();
 
         foreach($out as $key=>$val) {
-            $key = trim($key);
+            $key = strip_tags(trim($key));
             $val = trim($val);
 
             switch($key) {
@@ -2953,4 +2953,38 @@ function clean_query_string($query, $amp=true)
 
     return $str;
 }
+
+function get_device_change_url()
+{
+    $p = parse_url(G5_URL);
+    $href = $p['scheme'].'://'.$p['host'];
+    if(isset($p['port']) && $p['port'])
+        $href .= ':'.$p['port'];
+    $href .= $_SERVER['SCRIPT_NAME'];
+
+    $q = array();
+    $device = 'device='.(G5_IS_MOBILE ? 'pc' : 'mobile');
+
+    if($_SERVER['QUERY_STRING']) {
+        foreach($_GET as $key=>$val) {
+            if($key == 'device')
+                continue;
+
+            $key = strip_tags($key);
+            $val = strip_tags($val);
+
+            if($key && $val)
+                $q[$key] = $val;
+        }
+    }
+
+    if(!empty($q)) {
+        $query = http_build_query($q, '', '&');
+        $href .= '?'.$query.'&'.$device;
+    } else {
+        $href .= '?'.$device;
+    }
+
+    return $href;
+}
 ?>
\ No newline at end of file
diff --git a/mobile/tail.php b/mobile/tail.php
index ceecca3fd..44d88ff22 100644
--- a/mobile/tail.php
+++ b/mobile/tail.php
@@ -25,30 +25,8 @@ if (!defined('_GNUBOARD_')) exit; // 개별 페이지 접근 불가
 </div>
 
 <?php
-if(G5_DEVICE_BUTTON_DISPLAY && G5_IS_MOBILE) {
-    $seq = 0;
-    $p = parse_url(G5_URL);
-    $href = $p['scheme'].'://'.$p['host'];
-    if(isset($p['port']) && $p['port'])
-        $href .= ':'.$p['port'];
-    $href .= $_SERVER['PHP_SELF'];
-    if($_SERVER['QUERY_STRING']) {
-        $sep = '?';
-        foreach($_GET as $key=>$val) {
-            if($key == 'device')
-                continue;
-
-            $href .= $sep.$key.'='.$val;
-            $sep = '&amp;';
-            $seq++;
-        }
-    }
-    if($seq)
-        $href .= '&amp;device=pc';
-    else
-        $href .= '?device=pc';
-?>
-<a href="<?php echo $href; ?>" id="device_change">PC 버전으로 보기</a>
+if(G5_DEVICE_BUTTON_DISPLAY && G5_IS_MOBILE) { ?>
+<a href="<?php echo get_device_change_url(); ?>" id="device_change">PC 버전으로 보기</a>
 <?php
 }
 
diff --git a/tail.php b/tail.php
index 8418253c6..48c1e7103 100644
--- a/tail.php
+++ b/tail.php
@@ -38,30 +38,8 @@ if (G5_IS_MOBILE) {
 </div>
 
 <?php
-if(G5_DEVICE_BUTTON_DISPLAY && !G5_IS_MOBILE) {
-    $seq = 0;
-    $p = parse_url(G5_URL);
-    $href = $p['scheme'].'://'.$p['host'];
-    if(isset($p['port']) && $p['port'])
-        $href .= ':'.$p['port'];
-    $href .= $_SERVER['PHP_SELF'];
-    if($_SERVER['QUERY_STRING']) {
-        $sep = '?';
-        foreach($_GET as $key=>$val) {
-            if($key == 'device')
-                continue;
-
-            $href .= $sep.$key.'='.strip_tags($val);
-            $sep = '&amp;';
-            $seq++;
-        }
-    }
-    if($seq)
-        $href .= '&amp;device=mobile';
-    else
-        $href .= '?device=mobile';
-?>
-<a href="<?php echo $href; ?>" id="device_change">모바일 버전으로 보기</a>
+if(G5_DEVICE_BUTTON_DISPLAY && !G5_IS_MOBILE) { ?>
+<a href="<?php echo get_device_change_url(); ?>" id="device_change">모바일 버전으로 보기</a>
 <?php
 }