Technology Weblogging

Second change

A vulnerability was discovered with WordPress 1.2.1 and 1.3a, as detailed here and in a forum thread for WordPress, here. This was caused by the fact that an important system variable, siteurl is modified in wp-login.php if the application detects that the URI used to access wp-login.php has changed from what’s stored in the database.

As detailed in both of the above locations, there is usually more than one way to access a specific file, and accessing the file using different variations of URL results in a change to this value that could cause problems with the site. At a minimum, it could result in unnecessary updates to the database.

The current WordPress release was modified to lessen the amount of destructiveness of this vulnerability, but it hasn’t eliminated the problem completely. To fix the remaining vulnerability, I’ve removed the code that updates this value in the database from wp-login.php (though I’ve left the option in the database for now). Unfortunately, this leaves the original problem that served as reason for this code, which is to make it easier to move your WordPress weblog if you need to. Without this code, moving your weblog to another directory can make the administrative pages impossible to access. When I removed the vulnerability, I added back this problem.

To fix this original problem, I added SITEURL as a new parameter to the wp-config.php file, now renamed wf-config.php to differentiate it from the WordPress file. Now, when the WordPress weblog is moved, you can use a text editor to change this value:

define (’SITEURL’, ‘’);

I also modified the code in the functions.php file that loads siteurl from the database, setting the cached values to that of SITEURL from the wf-config.php file.

if (’siteurl’ == $option->option_name) {
$option->option_value = preg_replace(’|/+$|’, ‘’, SITEURL);

This is an interim fix, while the rest of the code is adjusted not to depend on this as an option loaded from the database. Once I’m sure this is so, I’ll remove the option from the database.

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