older versions of open cart & security

I've just bought a theme from template monster only to find out that I need to use version 1.5.3 which seems to be 2.5 years out of date.

I'm gussing that using this is a bad idea, right?

Do you have a list of security releases (I've searched but only find blog posts)?

d

Not any security issues that I can recall in the 1.5.3.x versions. However, there's plenty of bug fixes, that's for sure