diff --git a/wp-admin/includes/image.php b/wp-admin/includes/image.php
index 3cb7764afc..4ee59b99eb 100644
--- a/wp-admin/includes/image.php
+++ b/wp-admin/includes/image.php
@@ -134,27 +134,56 @@ function wp_generate_attachment_metadata( $attachment_id, $file ) {
 	}
 
 	if ( $support && ! empty( $metadata['image']['data'] ) ) {
-		$ext = '.jpg';
-		switch ( $metadata['image']['mime'] ) {
-		case 'image/gif':
-			$ext = '.gif';
-			break;
-		case 'image/png':
-			$ext = '.png';
-			break;
-		}
-		$basename = str_replace( '.', '-', basename( $file ) ) . '-image' . $ext;
-		$uploaded = wp_upload_bits( $basename, '', $metadata['image']['data'] );
-		if ( false === $uploaded['error'] ) {
-			$attachment = array(
-				'post_mime_type' => $metadata['image']['mime'],
-				'post_type' => 'attachment',
-				'post_content' => '',
-			);
-			$sub_attachment_id = wp_insert_attachment( $attachment, $uploaded['file'] );
-			$attach_data = wp_generate_attachment_metadata( $sub_attachment_id, $uploaded['file'] );
-			wp_update_attachment_metadata( $sub_attachment_id, $attach_data );
-			update_post_meta( $attachment_id, '_thumbnail_id', $sub_attachment_id );
+		// check for existing cover
+		$hash = md5( $metadata['image']['data'] );
+		$posts = get_posts( array(
+			'fields' => 'ids',
+			'post_type' => 'attachment',
+			'post_mime_type' => $metadata['image']['mime'],
+			'post_status' => 'inherit',
+			'posts_per_page' => 1,
+			'meta_key' => '_cover_hash',
+			'meta_value' => $hash
+		) );
+		$exists = reset( $posts );
+
+		if ( ! empty( $exists ) ) {
+			update_post_meta( $attachment_id, '_thumbnail_id', $exists );
+		} else {
+			$ext = '.jpg';
+			switch ( $metadata['image']['mime'] ) {
+			case 'image/gif':
+				$ext = '.gif';
+				break;
+			case 'image/png':
+				$ext = '.png';
+				break;
+			}
+			$basename = str_replace( '.', '-', basename( $file ) ) . '-image' . $ext;
+			$uploaded = wp_upload_bits( $basename, '', $metadata['image']['data'] );
+			if ( false === $uploaded['error'] ) {
+				$image_attachment = array(
+					'post_mime_type' => $metadata['image']['mime'],
+					'post_type' => 'attachment',
+					'post_content' => '',
+				);
+				/**
+				 * Filter the parameters for the attachment thumbnail creation.
+				 *
+				 * @since 3.9.0
+				 *
+				 * @param array $image_attachment An array of parameters to create the thumbnail.
+				 * @param array $metadata   Current attachment metadata.
+				 * @param array $uploaded   An array containing the thumbnail path and url.
+				 */
+				$image_attachment = apply_filters( 'attachment_thumbnail_args', $image_attachment, $metadata, $uploaded );
+
+				$sub_attachment_id = wp_insert_attachment( $image_attachment, $uploaded['file'] );
+				add_post_meta( $sub_attachment_id, '_cover_hash', $hash );
+				$attach_data = wp_generate_attachment_metadata( $sub_attachment_id, $uploaded['file'] );
+				wp_update_attachment_metadata( $sub_attachment_id, $attach_data );
+				update_post_meta( $attachment_id, '_thumbnail_id', $sub_attachment_id );
+			}
 		}
 	}