I have been lately browsing material icons from this site.
I started to notice that they don't have any free plans as such so you will have to buy the icons if you want to download them. But however I am concerned regarding the preview. I just had to inspect element in the browser and found out that there was a dynamically added style to a div element with the following background-image property:
Wow! I got the URL that leads me to the SVG icon! Then Save as > Download > icon.svg.
The above link might be updated later on as you can see parameters like
pair-Id and stuff. So you will have to go inspect yourself.
Since this can't be called a vulnerability, I am a bit hesitant to ask how such sites can display a preview without enabling frauds to steal their content.
There should be some way right? Is it impossible?