Solution 1:
Actually, this isn’t an issue you need to fix directly.
The problem originates from the WP Symposium plugin’s file. Do you have the latest version of the plugin installed? I haven’t reviewed the plugin code myself, but according to its download page, it’s only listed as compatible up to WordPress version 3.5.
Solution 2:
This warning appears because SQL queries should use ? placeholders for unescaped arguments. Since WordPress 3.5, the system now alerts you if this best practice is not followed.
Andrew Nacin, the lead developer for WordPress 3.5, explained this change in a blog post on make.wordpress.com
:
“This wasn’t a decision made lightly. We try to avoid pushing PHP notices onto the screens of users and developers. However, given the potential security risks, we wanted everyone to immediately review how they are running queries—and, of course, always prepare them properly.”