Hello,
I’ve seen similar things reported in the past and while the culprit looks like Quick Cache, it’s not.
If your site has malware causing spam to be injected into the HTML, then Quick Cache will end up caching that HTML (it caches whatever HTML is generated). If the malware stops injecting the spam into the HTML and you disable Quick Cache, it will look like the spam goes away (because Quick Cache stops serving the old cache file that included the spam).
My recommendation is to clear the Quick Cache cache and reload the site. Do you still see the spam there? If so, then I would disable Quick Cache, disable all other plugins, then re-enable Quick Cache. Is the spam still there? Most likely not (which would indicate that one of the other plugins you disabled is injecting the spam).
If even after disabling all plugins you still see the spam there, then I would recommend checking all the PHP files on your site, as those may have been compromised. You might need to delete and reinstall a clean copy of WordPress. Please see the WordPress Support Forum for further help.
