diff --git a/lib/FormatV2.php b/lib/FormatV2.php
index 7f1912fa..b7e749f9 100644
--- a/lib/FormatV2.php
+++ b/lib/FormatV2.php
@@ -56,7 +56,21 @@ class FormatV2
             return false;
         }
 
-        $cipherParams = $isComment ? $message['adata'] : $message['adata'][0];
+        $cipherParams = $isComment ? $message['adata'] : ($message['adata'][0] ?? null);
+
+        // Make sure the cipher parameters are a properly sized array.
+        if (!is_array($cipherParams) || count($cipherParams) < 8) {
+            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.
+        if (!is_string($message['ct']) ||
+            !is_string($cipherParams[0] ?? null) ||
+            !is_string($cipherParams[1] ?? null)) {
+            return false;
+        }
 
         // Make sure some fields are base64 data:
         // - initialization vector
@@ -119,6 +133,7 @@ class FormatV2
 
         // require only the key 'expire' in the metadata of pastes
         if (!$isComment && (
+            !is_array($message['meta']) ||
             count($message['meta']) === 0 ||
             !array_key_exists('expire', $message['meta']) ||
             count($message['meta']) > 1
diff --git a/lib/Request.php b/lib/Request.php
index 31233472..c1902b72 100644
--- a/lib/Request.php
+++ b/lib/Request.php
@@ -189,8 +189,13 @@ class Request
         foreach ($required_keys as $key) {
             $data[$key] = $this->getParam($key, $key === 'v' ? 1 : '');
         }
-        // forcing a cast to int or float
-        $data['v'] = $data['v'] + 0;
+        // forcing a cast to int or float, but only when the value is
+        // numeric; a non-numeric version is left untouched so the format
+        // validator rejects it with "Invalid data." instead of a fatal
+        // type error
+        if (is_numeric($data['v'])) {
+            $data['v'] = $data['v'] + 0;
+        }
         return $data;
     }
 
diff --git a/tst/FormatV2Test.php b/tst/FormatV2Test.php
index 2e13d8f5..b5dfca1b 100644
--- a/tst/FormatV2Test.php
+++ b/tst/FormatV2Test.php
@@ -72,4 +72,41 @@ class FormatV2Test extends TestCase
         $paste = Helper::getPaste();
         $this->assertFalse(FormatV2::isValid($paste), 'invalid meta key');
     }
+
+    public function testFormatV2ValidatorRejectsMalformedTypes()
+    {
+        // malformed input must yield "false" (Invalid data) rather than a
+        // fatal type error under strict_types
+        $paste          = Helper::getPastePost();
+        $paste['v']     = 'abc';
+        $this->assertFalse(FormatV2::isValid($paste), 'non-numeric version');
+
+        $paste          = Helper::getPastePost();
+        $paste['v']     = array();
+        $this->assertFalse(FormatV2::isValid($paste), 'array version');
+
+        $paste          = Helper::getPastePost();
+        $paste['ct']    = array('not', 'a', 'string');
+        $this->assertFalse(FormatV2::isValid($paste), 'non-string ciphertext');
+
+        $paste          = Helper::getPastePost();
+        $paste['meta']  = 'not-an-array';
+        $this->assertFalse(FormatV2::isValid($paste), 'non-array meta');
+
+        $paste          = Helper::getPastePost();
+        $paste['adata'][0] = 'not-an-array';
+        $this->assertFalse(FormatV2::isValid($paste), 'non-array cipher parameters');
+
+        $paste          = Helper::getPastePost();
+        $paste['adata'][0] = array();
+        $this->assertFalse(FormatV2::isValid($paste), 'empty cipher parameters');
+
+        $paste             = Helper::getPastePost();
+        $paste['adata'][0][0] = array();
+        $this->assertFalse(FormatV2::isValid($paste), 'non-string iv');
+
+        $comment           = Helper::getCommentPost();
+        $comment['ct']     = 42;
+        $this->assertFalse(FormatV2::isValid($comment, true), 'non-string comment ciphertext');
+    }
 }