XSS stands for Cross-Site Scripting. The correct abbreviation would naturally have been CSS, but that term is already assigned. But what does XSS mean? As the name says, script code is inserted from another site (Cross-Site) and it works like this: An attacker succeeds in inserting harmful JavaScript code into a page. Since it concerns client-side technology, this code is run on the client, thus on the respective website visitor's computer.

The main reason for the success of this type of an attack lies in the fact that data coming from the user is passed without checking. Here is an excerpt from the /html/ content.php file of Mambo 4.5 Stable 1.0.3, from the editContent() function:

$Returnid = mosGetParam( $_REQUEST, 'Returnid', 0 );

So far there is nothing unusual. The Returnid value is read from the superglobal $_Request array and stored in the $Returnid variable. You can see the mosGetParam() function from the classes/mambo.php file as evidence:

/**
* Utility...