A "Zero-day" security vulnerability has been found in a Wordpress image resizing library called TimThumb. A "library" is a section of code that other bits of code can call on to perform a common task. Therefore, this means that lots of disparate plugins rely on this one "library" to perform image resizing. That in turn means that while it is only this one library that has the issue, many Wordpress plugins are now at risk because they all use this library.