Slider, Gallery, and Carousel by MetaSlider < 3.27.9 - Admin+ Stored Cross Site Scripting

The plugin does not sanitise and escape some of its Gallery Image parameters, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup)

Add an image to a Gallery (via MetaSlider  > Gallery Beta) and put the following payload in the "Alt Text" setting: "><img src onerror=alert(/XSS/)>