Custom Image URL with plugin RSS Aggregator

Hi all, I am working with plugin WP RSS Aggregator. And I faced a problem that I want to import the featured image with the first image from post content. But the image url contains width parameter (e.g https://abc.com/v1/items/image1.jpg?s=300x), so that the featured image would be a small size. I want to filter the parameter (?s=300x) to make the image be a full size one. I have checked the plugin support but I found nothing about it. Thank you for any suggestions!!

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