Very cool that they detailed the entire attack; interesting stuff.
If you can upload executable content, you can do some nasty things. I was doing a pen test and found some outdated PHP help desk software via DirBuster on one of their web servers. I couldn't believe there was a exploit for it on Milw0rm. You just ran the PHP script from the command-line, specified an IP address and directory where the help desk app was installed, and instant shell.
I found the MySQL credentials in one of the PHP files, and I was able to write a simple PHP file that allowed me to execute arbitrary SQL queries. I got everything from the users table and John cracked a super weak administrator password hash in just a few seconds.
I got that box and another share on the network, but I wanted the domain. I think password expiration/complexity requirements saved them there