How safe is the Steam web browser?

[_o_OOOO_oo-Kanawha]

While browsing through the Railworks Workship I came across a scenario that needed a repaint. I inadvertedly clicked on the link without copying it to my normal web browser.
The repaint was hosted on Mediafire and suddenly my Steam web browser was flooded with full page adds I couln't get rid off because they seemed borderless and were without close icons. Also, Steam provided no Close item in the right click menu.

What browser engine is used by Steam and how secure is it?
Where do its cache, history, cookies and passwords reside so I can flush them?

Given the Steam identity thefts of late, I am worried about that built in browser. Can it be made more secure?

[peterhayes]

That was media fire NOT STEAM.
MF can cause quite a few issues on occasion.
The STEAM browser is very secure - if it wasn't all of our bank balances would be empty by now!
pH