[#security] Updated dependencies

Author: Chris Smith

composer.json

@@ -6,7 +6,8 @@
         "php": "^7.1.3",
         "guzzlehttp/guzzle": "^6.3",
         "illuminate/support": ">=5",
-        "symfony/http-foundation": "^4.3"
+        "symfony/http-foundation": "^4.3.8",
+        "symfony/mime": "^4.3.8"
     },
     "require-dev": {
         "phpunit/phpunit": "^7.5",