style.scss

ul.wp-block-rss { // The ul is needed for specificity to override the reset styles in the editor.
	list-style: none;
	padding: 0;

	// This needs extra specificity due to the reset mixin on the parent: https://github.com/WordPress/gutenberg/blob/a250e9e5fe00dd5195624f96a3d924e7078951c3/packages/edit-post/src/style.scss#L54
	&.wp-block-rss {
		box-sizing: border-box;
	}

	&.alignleft {
		/*rtl:ignore*/
		margin-right: 2em;
	}
	&.alignright {
		/*rtl:ignore*/
		margin-left: 2em;
	}
	&.is-grid {
		display: flex;
		flex-wrap: wrap;
		padding: 0;
		list-style: none;

		li {
			margin: 0 1em 1em 0;
			width: 100%;
		}
	}

	@include break-small {
		@for $i from 2 through 6 {
			&.columns-#{ $i } li {
				width: calc(( 100% / #{ $i } ) - 1em);
			}
		}
	}
}

.wp-block-rss__item-publish-date,
.wp-block-rss__item-author {
	display: block;
	font-size: 0.8125em;
}
.wp-block-rss {
	box-sizing: border-box;
	.wp-block-rss {
		margin: 0;
		border: 0;
	}
}