Path empty - cleaning fails

This doesn't really address your issue, but it provides some context:

JS/Sinowal-V is a malicious javascript embedded in web pages, and is commonly found on fraud/phishing pages and SEO poison pages.  It attempts to load malware onto your computer via a hidden iFrame injected via the script into the web page, that points to the actual malicious site.

The place where I've seen the behaviour you're experiencing is when Safari caches the malicious file, on-access detects it, safari clears it from the cache, and then re-loads it.  The detection now still exists, but the original path name of the first cache file no longer points to a file on the system.  The back end SHOULD still list the new path, but I too have seen instances where it is blank instead.

Hopefully this is enough of a bug description for the developer folk to track down; I suspect that it's still not enough to recreate the issue however.

On the plus side, purging your web cache should clear all copies of this malware.  If the item still exists in Quarantine after that, please remove it from the list and then run a custom scan over your ~/Library/Caches folder.

This doesn't really address your issue, but it provides some context:

JS/Sinowal-V is a malicious javascript embedded in web pages, and is commonly found on fraud/phishing pages and SEO poison pages.  It attempts to load malware onto your computer via a hidden iFrame injected via the script into the web page, that points to the actual malicious site.

The place where I've seen the behaviour you're experiencing is when Safari caches the malicious file, on-access detects it, safari clears it from the cache, and then re-loads it.  The detection now still exists, but the original path name of the first cache file no longer points to a file on the system.  The back end SHOULD still list the new path, but I too have seen instances where it is blank instead.

Hopefully this is enough of a bug description for the developer folk to track down; I suspect that it's still not enough to recreate the issue however.

On the plus side, purging your web cache should clear all copies of this malware.  If the item still exists in Quarantine after that, please remove it from the list and then run a custom scan over your ~/Library/Caches folder.