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Google Analytics Counter Tracker WordPress Plugin unauthenticed PHP
Object injection vulnerability
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Remco Vermeulen, July 2016

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Abstract
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A PHP Object injection vulnerability was found in Google Analytics
Counter Tracker, which can be used by an unautenthicated user to
instantiated arbitrary PHP Objects. Using this vulnerability it is
possible to execute arbitrary PHP code.

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OVE ID
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OVE-20160712-0035

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Tested versions
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This issue was succesfully tested on the Google Analytics Counter
Tracker [2] WordPress Plugin version 3.1.5.

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Fix
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This issue has been addressed in Google Analytics Counter Tracker
version 3.5.1 [3].

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Introduction
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Google Analytics Counter Tracker [2]  analyse the visitors hits on you
website and display it graphically. A PHP Object injection [4]
vulnerability was found in Google Analytics Counter Tracker, which can
be used by an unautenthicated user to instantiated arbitrary PHP
Objects.

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Details
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This issue is possible due to an unsafe call to unserialize() in the
proccessRequest() method. The input is taken directly from the
wpadm_ga_request cookie as can be seen in the following code fragment:

class.wpadm-ga.php:

protected static function proccessRequest() {
	$request_name = self::REQUEST_PARAM_NAME;
	$params = unserialize(base64_decode($_POST[$request_name]));
	
	$v = self::verifySignature($params['sign'],
get_option('wpadm_ga_pub_key'), md5(serialize($params['data'])));

It has been confirmed that this issues can be used to execute arbitrary
PHP code.
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References
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[1]
https://sumofpwn.nl/advisory/2016/google_analytics_counter_tracker_wordpress_plugin_unauthenticed_php_object_injection_vulnerability.html
[2] https://wordpress.org/plugins/analytics-counter/
[3] https://downloads.wordpress.org/plugin/analytics-counter.zip
[4] https://www.owasp.org/index.php/PHP_Object_Injection