diff --git a/cake/libs/controller/components/security.php b/cake/libs/controller/components/security.php
index c267c6ce189..7e5b3b28f3d 100644
--- a/cake/libs/controller/components/security.php
+++ b/cake/libs/controller/components/security.php
@@ -618,10 +618,15 @@ function _validatePost(&$controller) {
 		}
 		unset($check['_Token']);
 
+		$locked = str_rot13($locked);
+		if (preg_match('/(\A|;|{|})O\:[0-9]+/', $locked)) {
+			return false;
+		}
+
 		$lockedFields = array();
 		$fields = Set::flatten($check);
 		$fieldList = array_keys($fields);
-		$locked = unserialize(str_rot13($locked));
+		$locked = unserialize($locked);
 		$multi = array();
 
 		foreach ($fieldList as $i => $key) {
diff --git a/cake/tests/cases/libs/controller/components/security.test.php b/cake/tests/cases/libs/controller/components/security.test.php
index 883f1c810b9..bbd51410041 100644
--- a/cake/tests/cases/libs/controller/components/security.test.php
+++ b/cake/tests/cases/libs/controller/components/security.test.php
@@ -608,6 +608,30 @@ function testValidatePostFormHacking() {
 		$result = $this->Controller->Security->validatePost($this->Controller);
 		$this->assertFalse($result, 'validatePost passed when key was missing. %s');
 	}
+
+/**
+ * Test that objects can't be passed into the serialized string. This was a vector for RFI and LFI 
+ * attacks. Thanks to Felix Wilhelm
+ *
+ * @return void
+ */
+	function testValidatePostObjectDeserialize() {
+		$this->Controller->Security->startup($this->Controller);
+		$key = $this->Controller->params['_Token']['key'];
+		$fields = 'a5475372b40f6e3ccbf9f8af191f20e1642fd877';
+
+		// a corrupted serialized object, so we can see if it ever gets to deserialize
+		$attack = 'O:3:"App":1:{s:5:"__map";a:1:{s:3:"foo";s:7:"Hacked!";s:1:"fail"}}';
+		$fields .= urlencode(':' . str_rot13($attack));
+
+		$this->Controller->data = array(
+			'Model' => array('username' => 'mark', 'password' => 'foo', 'valid' => '0'),
+			'_Token' => compact('key', 'fields')
+		);
+		$result = $this->Controller->Security->validatePost($this->Controller);
+		$this->assertFalse($result, 'validatePost passed when key was missing. %s');
+	}
+
 /**
  * Tests validation of checkbox arrays
  *