Image breaks out of container in meta box

[wpmark]

When a user is using the Classic Editor, the generated image in the Social Image meta box breaks out of its container. This is because max-width: 100%; is not being set which when the block editor is used is added with the following:

.block-editor__container img {
    max-width: 100%;
    height: auto;
}

The solution here is to add max-width: 100%; to the img.ssi-image rule in hd-ssi-admin.css.