Wordpress: Blank page when trying to post

Source: Blog.taragana.com
The hacker was able to press a .txt file in the /tmp directory.

The hacker exploited several WordPress vulnerabilities in administrative scripts to gain full access to the website (as permitted to apache user), including the ability to upload & run scripts, delete any file owned by apache user, view the file and directories etc.

This is a full disclosure on the how the site was hacked and how I detected and removed the hack along with few comments on the state of WordPress security. I added a WordPress plugin and made modifications to prevent any such hacking attempts in future using WordPress. This is a must read for WordPress bloggers.

How the site hacking was detected?
The website was normal. However when I tried to publish or even save a post, it simply showed a blank page. The post was never published or even saved. I knew something was wrong.
My first suspect were couple of plugins which contacted external servers after a publish. I disabled them. I also disabled the ping sites as they were sometimes known to cause problems. None of that helped. I progressively disabled all of the plugins. Even with all the plugins disabled, the post wouldn’t publish. I was left with only one option.
I decided to trace WordPress code to find out the cause of error. I started with the file for post submission - post.php. I found something startling with WordPress code which seriously undermines its security, a flawed design choice but more on it later. post.php calls admin.php which calls wp-config.php which in turn calls wp-settings.php. wp-settings is an interesting file. This file isn’t just about settings. It loads tons of files, loads and executes the plugins and more. The problem was, as I originally suspected, in the plugins but which one? The code which loads the plugins in WordPress is:
if ( get_option('active_plugins') ) {
$current_plugins = get_option('active_plugins');
if ( is_array($current_plugins) ) {
foreach ($current_plugins as $plugin) {
if ('’ != $plugin && file_exists(ABSPATH . PLUGINDIR . ‘/’ . $plugin))
include_once(ABSPATH . PLUGINDIR . ‘/’ . $plugin);
}
}
}
The active plugins, as you can see, are loaded directly with include_once. How do I find the plugin which while loading is causing the script to die?I added simple syslog() statements before and after the plugin. However it generated copious output from all the traffic.Remember I was debugging on a heavily trafficked live site. So I added a define in post.php which I was checking before doing a syslog.

The debugging code was:
if ('’ != $plugin && file_exists(ABSPATH . ‘wp-content/plugins/’ . $plugin)) {if(defined(’TG_ADMIN’)) syslog(LOG_ALERT, “Loading $plugin…”);include_once(ABSPATH . ‘wp-content/plugins/’ . $plugin);if(defined(’TG_ADMIN’)) syslog(LOG_ALERT, “Loaded $plugin…”);}

The result was surprising. The first plugin loaded was not even a plugin I knew existed, let alone use it. It was named ro8kbsmawge.txt.

The full path to the plugin
was /../../../../../../../../../../../../../../../../../../tmp/ro8kbsmawge.txt

Effectively the file path was /tmp/ro8kbsmawge.txt. A telltale sign of this hacker is the presence of the file ro8kbsmawge.txt in your tmp directory.

I renamed the file and the problem was solved for now. I could publish posts finally. However my site was still not secure against future attacks. I will detail next at how I secured my site and provide more information on the perpetrator and how the site was hacked in the first place.

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