The Code Snippets WordPress plugin before 3.10.0 does not sanitise and escape a user-supplied parameter before using it in a SQL query in some of its snippet-migration import endpoints, which are accessible to any user holding site-administration capabilities; on a WordPress Multisite network those belong to subsite Administrators, allowing a subsite Administrator who is not a network Super Admin to perform UNION-based SQL injection against shared network tables and disclose network-wide data such as other users' password hashes.
The Code Snippets plugin for WordPress is vulnerable to PHP Code Injection in all versions up to, and including, 3.9.1. This is due to the plugin's use of extract() on attacker-controlled shortcode attributes within the evaluateshortcodefromflatfile method, which can be used to overwrite the $filepath variable and subsequently passed to requireonce. This makes it possible for authenticated attackers, with Contributor-level access and above, to execute arbitrary PHP code on the server via the [codesnippet] shortcode using PHP filter chains granted they can trick an administrator into enabling the "Enable file-based execution" setting and creating at least one active Content snippet.