I’m having the same issue. I spoke with Shopify and they disregarded saying that it is most likely the themes third party and to contact them. However, when looking at other forums and doing a quick google search there are thousands of Shopify accounts affected.
This is in fact a malware.
I called my domain company and they did confirm this site was generating malware but due to Shopify’s limitations on providing file transfer privileges they could not delete or remove the malware and stated Shopify has to do it.
I’m contacting Shopify again today to see if anything can be done.
