Yes, but it’s nearly impossible if it has strong protection. Most cloud services contain multi-layered endpoint security that makes it nearly impossible for hackers to find vulnerabilities they can exploit. While a threat actor could theoretically hack into an antivirus cloud service, each company on my list uses strong endpoint security to keep their cloud data safe.
It’s still a great idea to regularly backup your files to a cloud, or even locally just in case. That said, the chances of your cloud-based antivirus being hacked are almost nonexistent.