The issue occurs on Opera 45.0.2552.812 Stable Linux 64-bit with browser identification
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36 OPR/45.0.2552.812
A web shop (will not tell the name so as not to compromise them in case this is an issue on my side) has a field for entering credit card information (name, expiration date, cvc). When I click any of the fields, Opera displays a combobox-style dropwdown below the field reading "Payment not secure!". At the same time I see a "Content blocked" message in the right end of the address bar. When I click that message and choose to enable said insecure content, I can see that the page is not HTTPS, and clicking the globe in the left part of the address bar, the attached popup is displayed.
What does the information mean and should I refrain from making a payment on that website?
Attached screenshot: https://ibin.co/3QBcZNR12iG3.png
The "Payment not secure!" warning appears only after I enable the insecure content in the address bar. Until I do it, thee is no warning whatsoever when entering information into the credit card fields.