Getting my site here being used for spamming it seems

[Zegnåt]

See the URL it points to?

It might be that someone tries to hack your site, or someone made a mistake in their system. No harm done, GetSimple shouldn’t be that easy a target. It just offers them just your 404, so no harm done.

This is the 3rd one this weekend from different sites.

Take a look at the IPs. If they are of a certain range, or even the same all the time, you could block them from the server in your HTACCESS-file. Another possibility would be to block them in the HTACCESS-file when the page request ends in “/SpryAssets/inbox.txt???”, assuming all use this same system to target your website.

Also the 404 error page email is showing code, is this a bug?

Yes, the emailer is flawed and will be removed in the next version of GetSimple.