Squarespace triggering anti-virus warnings - anyone else?

Hi

I've had a customer report that clicking on a link to our squarespace site via a squarespace marketing email is triggering a warning from WebShield anti-virus software. Here's the message the customer is receiving:

"Web Shield has detected a variety of malicious items on mgcp03.engage.squarespace-mail.com that might attempt to install harmful programs on your computer that can modify and delete your files, change your browser settings, or steal information (i.e. photos, passwords, messages, credit cards)"

Has anyone else had reports of this happening? It's the first time someone has contacted us about this, but of course it could have been happening for a while and this is just the first we've heard.

Thanks