fix: check adata array size for pastes

lib/FormatV2.php

@@ -39,7 +39,7 @@ class FormatV2
             $required_keys[] = 'meta';
         }
 
-        // Make sure no additionnal keys were added.
+        // Make sure no additional keys were added.
         if (count(array_keys($message)) !== count($required_keys)) {
             return false;
         }
@@ -63,6 +63,11 @@ class FormatV2
             return false;
         }
 
+        // Make sure the adata parameters of pastes are a properly sized array,
+        if (!$isComment && count($message['adata']) !== 4) {
+            return false;
+        }
+
         // Make sure the ciphertext and the cipher parameters used in the
         // string operations below are actually strings, so that malformed
         // input yields "Invalid data." instead of a fatal type error.