Global Styles: Fix for third-party blocks

src/wp-includes/global-styles-and-settings.php

@@ -218,14 +218,18 @@ function wp_add_global_styles_for_blocks() {
 			continue;
 		}
 
+		$stylesheet_handle = 'global-styles';
 		if ( isset( $metadata['name'] ) ) {
-			$block_name = str_replace( 'core/', '', $metadata['name'] );
 			/*
 			 * These block styles are added on block_render.
 			 * This hooks inline CSS to them so that they are loaded conditionally
 			 * based on whether or not the block is used on the page.
 			 */
-			wp_add_inline_style( 'wp-block-' . $block_name, $block_css );
+			if ( str_starts_with( $metadata['name'], 'core/' ) ) {
+				$block_name        = str_replace( 'core/', '', $metadata['name'] );
+				$stylesheet_handle = 'wp-block-' . $block_name;
+			}
+			wp_add_inline_style( $stylesheet_handle, $block_css );
 		}
 
 		// The likes of block element styles from theme.json do not have  $metadata['name'] set.
@@ -242,8 +246,11 @@ function ( $item ) {
 				)
 			);
 			if ( isset( $result[0] ) ) {
-				$block_name = str_replace( 'core/', '', $result[0] );
-				wp_add_inline_style( 'wp-block-' . $block_name, $block_css );
+				if ( str_starts_with( $result[0], 'core/' ) ) {
+					$block_name        = str_replace( 'core/', '', $result[0] );
+					$stylesheet_handle = 'wp-block-' . $block_name;
+				}
+				wp_add_inline_style( $stylesheet_handle, $block_css );
 			}
 		}
 	}