diff --git a/CHANGELOG.md b/CHANGELOG.md
index c6c938ca..b431b5b0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,9 @@
 
 ## 1.7.2 (not yet released)
 * ADDED: Allow use of `shortenviayourls` in query parameters (#1267)
+* ADDED: Input sanitation to some not yet filtered query and server parameters
 * CHANGED: "Send" button now labeled "Create" (#946)
+* CHANGED: drop some PHP < 5.6 fallbacks, minimum version is PHP 7.3 as of release 1.6.0
 * FIXED: Add cache control headers also to API calls (#1263)
 * FIXED: Shortened paste URL does not appear in email (#606)
 
diff --git a/lib/Model/AbstractModel.php b/lib/Model/AbstractModel.php
index 2e77cef9..de7b9a02 100644
--- a/lib/Model/AbstractModel.php
+++ b/lib/Model/AbstractModel.php
@@ -108,7 +108,7 @@ abstract class AbstractModel
         $this->_data = $data;
 
         // calculate a 64 bit checksum to avoid collisions
-        $this->setId(hash(version_compare(PHP_VERSION, '5.6', '<') ? 'fnv164' : 'fnv1a64', $data['ct']));
+        $this->setId(hash('fnv1a64', $data['ct']));
     }
 
     /**
diff --git a/lib/Request.php b/lib/Request.php
index ef6c7043..94202744 100644
--- a/lib/Request.php
+++ b/lib/Request.php
@@ -82,13 +82,10 @@ class Request
      */
     private function getPasteId()
     {
-        // RegEx to check for valid paste ID (16 base64 chars)
-        $pasteIdRegEx = '/^[a-f0-9]{16}$/';
-
         foreach ($_GET as $key => $value) {
-            // only return if value is empty and key matches RegEx
-            if (($value === '') and preg_match($pasteIdRegEx, $key, $match)) {
-                return $match[0];
+            // only return if value is empty and key is 16 hex chars
+            if (($value === '') && strlen($key) === 16 && ctype_xdigit($key)) {
+                return $key;
             }
         }
 
@@ -121,7 +118,13 @@ class Request
                 }
                 break;
             default:
-                $this->_params = $_GET;
+                $this->_params = filter_var_array($_GET, array(
+                    'deletetoken'      => FILTER_SANITIZE_SPECIAL_CHARS,
+                    'jsonld'           => FILTER_SANITIZE_SPECIAL_CHARS,
+                    'link'             => FILTER_SANITIZE_URL,
+                    'pasteid'          => FILTER_SANITIZE_SPECIAL_CHARS,
+                    'shortenviayourls' => FILTER_SANITIZE_SPECIAL_CHARS,
+                ), false);
         }
         if (
             !array_key_exists('pasteid', $this->_params) &&
@@ -209,9 +212,8 @@ class Request
      */
     public function getHost()
     {
-        return array_key_exists('HTTP_HOST', $_SERVER) ?
-            htmlspecialchars($_SERVER['HTTP_HOST']) :
-            'localhost';
+        $host = array_key_exists('HTTP_HOST', $_SERVER) ? filter_var($_SERVER['HTTP_HOST'], FILTER_SANITIZE_URL) : '';
+        return empty($host) ? 'localhost' : $host;
     }
 
     /**
@@ -222,10 +224,8 @@ class Request
      */
     public function getRequestUri()
     {
-        return array_key_exists('REQUEST_URI', $_SERVER) ?
-        htmlspecialchars(
-            parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH)
-        ) : '/';
+        $uri = array_key_exists('REQUEST_URI', $_SERVER) ? filter_var($_SERVER['REQUEST_URI'], FILTER_SANITIZE_URL) : '';
+        return empty($uri) ? '/' : $uri;
     }
 
     /**
@@ -275,10 +275,9 @@ class Request
         }
 
         // advanced case: media type negotiation
-        $mediaTypes = array();
         if ($hasAcceptHeader) {
-            $mediaTypeRanges = explode(',', trim($acceptHeader));
-            foreach ($mediaTypeRanges as $mediaTypeRange) {
+            $mediaTypes = array();
+            foreach (explode(',', trim($acceptHeader)) as $mediaTypeRange) {
                 if (preg_match(
                     '#(\*/\*|[a-z\-]+/[a-z\-+*]+(?:\s*;\s*[^q]\S*)*)(?:\s*;\s*q\s*=\s*(0(?:\.\d{0,3})|1(?:\.0{0,3})))?#',
                     trim($mediaTypeRange), $match
@@ -287,6 +286,9 @@ class Request
                         $match[2] = '1.0';
                     } else {
                         $match[2] = (string) floatval($match[2]);
+                        if ($match[2] === '0.0') {
+                            continue;
+                        }
                     }
                     if (!isset($mediaTypes[$match[2]])) {
                         $mediaTypes[$match[2]] = array();
@@ -296,9 +298,6 @@ class Request
             }
             krsort($mediaTypes);
             foreach ($mediaTypes as $acceptedQuality => $acceptedValues) {
-                if ($acceptedQuality === '0.0') {
-                    continue;
-                }
                 foreach ($acceptedValues as $acceptedValue) {
                     if (
                         strpos($acceptedValue, self::MIME_HTML) === 0 ||
diff --git a/tst/Bootstrap.php b/tst/Bootstrap.php
index 3af4db0a..7f4caa32 100644
--- a/tst/Bootstrap.php
+++ b/tst/Bootstrap.php
@@ -696,7 +696,7 @@ class Helper
      */
     public static function getPasteId()
     {
-        return version_compare(PHP_VERSION, '5.6', '<') ? hash('fnv164', self::$pasteV2['ct']) : self::$pasteid;
+        return self::$pasteid;
     }
 
     /**