Description
WordPress Plugin Membership Simplified is prone to a vulnerability that lets attackers download arbitrary files because the application fails to sufficiently verify user-supplied input. This may allow an attacker to gain access to sensitive information, which may aid in launching further attacks. WordPress Plugin Membership Simplified version Beta 1.58 is vulnerable; prior versions may also be affected.
Remediation
Edit the source code to ensure that input is properly verified or disable the plugin until a fix is available
References
http://www.vapidlabs.com/advisory.php?v=187
https://www.alien-within.com/wordpress-plugin-membership-simplified-v1-58-arbitrary-file-download/
http://www.openwall.com/lists/oss-security/2017/03/14/5