Hey Dhayman,
As far as I can understand, they were using a javascript exploit in the CMS which gives them the ‘page’ they wanted. A lot of CMS’ use .htaccess re-write rules as well, which will re-write the URL to something more SEO friendly. By doing this, the spammer would only have to title the page (typically done when creating the page – asks for title, description, content).
As far as the rest, I only know because several of my sites are being hit with comment spam (NON-Blog sites) which are self-created php scripts and form-based.
They find the inputboxes and then spam them hoping for content. For comments, they actually tested out the comment manually and when they saw it worked – they put it into their automatic adder. This adder also queries the site for additional places to spam and spams them as well.