Sed, have you tried
1. Rebooting your computer, and cleaning cookies and cache? Also, do an online virus scan https://www.trendmicro.com/en_ca/forHome/products/housecall.html as it can't hurt.
2. Have you tried using Brave browser?
3. A warning of that type generally means there's something about the file that the website is reacting to, and it can be many things.
The fact there are no other reports of this strongly suggests it's a local problem between your machine and WC.
Try 1, 2 and 3 above. If they don't solve the problem, try uploading a simple screenshot to my January thread, and report what happens. OK?
The IT guys are on weekend footing, and tbh this appears to be an individual problem so they might leave it until Monday. I'll leave a message on the chance they'll see it. 
edit: Got an answer from IT. They're asking you to email the file to them for analysis: here's the email address: services@stardock.com