Added json_encode/json_decode to list of insecure functions

Magento2/Sniffs/Security/InsecureFunctionSniff.php

@@ -28,15 +28,17 @@ class InsecureFunctionSniff extends ForbiddenFunctionsSniff
         'assert' => null,
         'create_function' => null,
         'exec' => null,
+        'json_decode' => 'injection \Magento\Framework\Serialize\SerializerInterface to your construct and unserialize',
+        'json_encode' => 'injection \Magento\Framework\Serialize\SerializerInterface to your construct and serialize',
         'md5' => 'improved hash functions (SHA-256, SHA-512 etc.)',
         'passthru' => null,
         'pcntl_exec' => null,
         'popen' => null,
         'proc_open' => null,
-        'serialize' => '\Magento\Framework\Serialize\SerializerInterface::serialize',
+        'serialize' => 'injection \Magento\Framework\Serialize\SerializerInterface to your construct and serialize',
         'shell_exec' => null,
         'system' => null,
-        'unserialize' => '\Magento\Framework\Serialize\SerializerInterface::unserialize',
+        'unserialize' => 'injection \Magento\Framework\Serialize\SerializerInterface to your construct and unserialize',
         'srand' => null,
         'mt_srand'=> null,
     ];

Magento2/Tests/Security/InsecureFunctionUnitTest.inc

@@ -27,3 +27,7 @@ pcntl_exec('path/goes/here');
 srand();
 
 mt_srand();
+
+json_encode([]);
+
+json_decode('[]');

Magento2/Tests/Security/InsecureFunctionUnitTest.php

@@ -40,6 +40,8 @@ public function getWarningList()
             25 => 1,
             27 => 1,
             29 => 1,
+            31 => 1,
+            33 => 1
         ];
     }
 }