Linked images in posts – remove hover effect

I have a problem with a gray rectangle appearing behind linked images in my posts. The rectangle appears as a hover effect, on those images that include a link. I assume this has to do with the default theme styling for elements inside a post that include a link. When I hover over a piece of text that also includes a link, the background of that piece of text becomes gray (I have set it that way, as the accent colour, and that’s all good, just not with images). The images in the posts then inherit this style, but it looks weird for images. The same problem appears with the icons at the end of each post from the plugin Simple Share Buttons. The icons are considered as a linked element of the post and on hover a gray rectangle appears over them as well. How can I remove the hover effect for linked images in posts only?
Thank you