The Responsive Lightbox & Gallery WordPress plugin before 2.5.2 use the Swipebox library which does not validate and escape title attributes before outputting them back in a page/post where used, which could allow users with the contributor role and above to perform Stored Cross-Site Scripting attacks.
https://wpscan.com/vulnerability/1862b4a6-5570-48a4-9b09-f9659eb0e9e3/