For those of you using Joomla! you will hopefully have signed up to the Joomla! Security Mailing List (If not please do this now on the Download Page at Joomla.org) and received notification that the latest version - 1.5.8 - has been released.

What you might not know is that there are some quite major effects you may experience from upgrading to 1.5.8 if you use HTML within your content (for example, to display google gadgets or banners from other sites, etc) which means they will no longer display!

Why is this?  In a word .. Filtering

Well, a filtering system has always been in existance in Joomla 1.5.x, but never really strictly enforced when it comes to content.  So, what do we mean by filtering?

When it comes to HTML, there is the good, the bad and the ugly!  Normal HTML coding for text styling, alignment and so forth is fine, that's the good code!  Bad coding can potentially be used to do harm, but in most cases is quite innocent - for example using the tag to display scripted content.  The Ugly HTML code can potentially do nasty things to your website ... which is why the filtering system has been tightened up.

The filtering system in Joomla allows you to set, by User Access Group, at which levels you want to strip out

a) All code,

b) All code containing tags or codes on the "blacklist", or

c) Only allow the tags I specify in the "whitelist"

If you want to read in depth about filtering there is some information on the Joomla Documentation Pages which you can find here, if you want to know what to do about it to make your code work, read on!