Input validation vulnerability in Popup Box – Best WordPress Popup Plugin 3.8.7

The Popup Box – Best WordPress Popup Plugin is vulnerable to a type of attack called Stored Cross-Site Scripting for all versions up to 3.8.7. This type of attack allows people with administrator access to inject malicious code into pages of the Plugin. This code would then be executed when any user visits those pages. This vulnerability only affects multi-site installations and installations with disabled unfiltered_html.