A cross-site scripting (XSS) vulnerability in Monstra CMS v3.0.4 allows attackers to execute arbitrary web scripts or HTML via a crafted payload injected into the Themes parameter at index.php.
Monstra CMS through 3.0.4 allows remote authenticated users to take over arbitrary user accounts via a modified login parameter to an edit URI, as demonstrated by login=victim to the users/21/edit URI.
Monstra CMS through 3.0.4 has an incomplete "forbidden types" list that excludes .php (and similar) file extensions but not the .pht or .phar extension, which allows remote authenticated Admins or Editors to execute arbitrary PHP code by uploading a file, a different vulnerability than CVE-2017-18048.