Index: wp-admin/async-upload.php
===================================================================
--- wp-admin/async-upload.php	(revision 58784)
+++ wp-admin/async-upload.php	(working copy)
@@ -74,7 +74,7 @@
 							}
 							?>
 							<span class="media-item-copy-container copy-to-clipboard-container edit-attachment">
-								<button type="button" class="button button-small copy-attachment-url" data-clipboard-text="<?php echo $file_url; ?>"><?php _e( 'Copy URL to clipboard' ); ?></button>
+								<button type="button" class="button button-small copy-attachment-url" data-clipboard-text="<?php echo esc_url( $file_url ); ?>"><?php _e( 'Copy URL to clipboard' ); ?></button>
 								<span class="success hidden" aria-hidden="true"><?php _e( 'Copied!' ); ?></span>
 							</span>
 						</div>