I have added images to products and the file uploader seems to add a red pixel into the image in the bottom right hand corner

That's interesting. I've never seen this before. Do you see this in a "private" or "incognito" window as well?

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It is visible in private windows as well -

The red pixel is added to the image when it is added to the product

Here is what happens when you add an additional image

That's odd. I can't think of anything in Hotcakes that would do this. This is why I asked about incognito, because this appears to be environmental in some way. I'm thinking first of browser plugin(s), but then anything else about the website implementation itself (other extensions, handlers, etc).

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It seems you have not correctly licensed Image Resizer: https://stackoverflow.co...72/image-appears-red-dot 
This happens if you enable a plugin that is not part of the "Essential Edition" https://imageresizing.net/plugins/editions/free 

The Image Resizer feature has been implemented in Hotcakes for years and I've never heard of this happening before. I'm guessing you're also using another module that has installed a newer version of Image Resizer. The version that currently is included in Hotcakes is 3.4.2.

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