He's joking mostly. He uploaded a webshell through the very poorly designed system that was in use. A webshell just runs whatever command it's given on a the machine its located and returns the results.
Probably this. I'm extremely left leaning but even I know vice is absolute dogshit. I used to work in the tar sands with my brother's, and once a year we have a tradition of watching the Vice tar sands "documentary" to laugh at how wildly inaccurate and ill-informed it is.
...custom 0day html script...?
Who is this guy? Batman?
Can anybody explain how an html 0day might be able to pwn a php file uploader?
That sounds terrifying... but at least I can be somewhat reassured that nobody is going to waste that on my wordpress installation...
[0] https://web.archive.org/web/20180508063705/http://5.61.27.15...