Does anyone remember any paths to files that would let you know what version of Umbraco that site is on, without having access to the backoffice?

Check out this from slide 37 onwards https://web.archive.org/web/20211102114643/https://www.perplex.nl/media/107928/codegarden-18-umbraco-security.pdf

cheers mate

I used to do MD5 hashes on certain public file/paths to try to detect an accurate version. Useful to our agency when a potential customer was enquiring about an upgrade. Which was one of the reasons I maintained the md5sums on my archive for as long as I did: http://code.leekelleher.com/umbraco/archive/