Tuesday, May 31, 2016

A File Upload Vulnerability barrage

I noticed a series of Wordpress/Joomla file upload attacks from a single IP address / attacker in a short period of time. Some of the requests were listed here. What I found interesting was not the fact that most were well known Wordpress vulnerabilities that are still unpatched by many web administrators. What I found interesting was the methodology of the malicious actor. It's likely what they have written is some sort of script/automated scanning tool, perhaps even a botnet or something that is doing this automatically. I envision that the code/script doing this probably has an array or list of well known Wordpress file upload vulnerabilities. It's probably a flexible dynamic list so that as soon as the attacker hear's about a new Wordpress file upload vulnerabilty, he can literally just add a URL path and a post parameter for the file name, and the script/botnet will probably just start scanning and attacking the internet trying to upload malicious files. Then there is likely a follow-up script that runs shortly after that connects to the uploaded backdoors and validates which ones were successful or not. In all the cases below the attacker uploads the same malicious file/name upfilees.php so that the attacker can easily go back later and determine if this was a device they compromised or not. The backdoor is probably a web shell that gives them full access to the web server's file system and the ability to run commands against the web server. Below I did my best to research a few of the attacks seen in this cycle and explain a bit.


In the above HTTP Post, there were 2 parameters that started with yiw. This indicates that the attacker is likely trying to explpoit the Beauty & Clean Theme File Upload Wordpress Vulnerability which is literally as simple as posting your backdoor file to the contact field via the sendmail action. If it succeeds, your file has been uploaded to the web server.


In the next HTTP Post, the attacker is likely attempting to exploit the Event Calendar Arbitrary Wordpress File Upload Vulnerability which is also as simple as passing the file you wanted uploaded as a post parameter to the uploadify.php page. Again, if successful, the attacker just uploaded a php web page to your server and can now do whatever they please.


In the next HTTP Post, the attacker is trying to exploit the tinybrowser Remote File Upload Joomla Vulnerability which is another simple vulnerability that involves posting the file you want uploaded as a parameter to the upload_file.php page. We're getting a bit repetitive and non-creative in these vulnerabilities, aren't we?


In the next HTTP Post, the attacker is trying to exploit the RevSlider Wordpress File Upload Vulnerability which again requires nothing more than chosing the right action parameter and posting the file, and guess what the web server will be compromised with a nice php backdoor. Oops.

POST /sites/all/libraries/elfinder/php/connector.minimal.php

In the next HTTP Post, the attacker appears to just be looking for poorly configured systems that have purposely enabled the ELFinder File Manager feature which allows you to remotely manage your web server's file system. Hmmm, can that be exploited? Yep, just post the upload command and your backdoor, and the attacker is in business.

POST /license.php

The final attack, I believe may be just a standard filename/location that certain attackers or botnets use to exploit systems. They probably exploited this server at some point, and added a backdoor called 'license.php' which allows arbirary file upload. So this attacker is just taking advantage of another attacker's prior compromise of this device. Easy pickings if it exists.

Wordpress & Joomla plugins should not be trusted (like anything else for that matter) and should only be added if absolutely needed. If you do need them, then you better be certain to keep them patched and updated. If you have a plugin that is really not necessary, please, please, please remove those extraneous plugins as otherwise they're going to open up huge ugly gaping holes in your security posture.

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1 comment:

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