Index: src/wp-admin/js/common.js
===================================================================
--- src/wp-admin/js/common.js	(revision 41847)
+++ src/wp-admin/js/common.js	(working copy)
@@ -307,6 +307,7 @@
 		$sortables = $('.meta-box-sortables'),
 		wpResponsiveActive = false,
 		$adminbar = $( '#wpadminbar' ),
+		adminReadonlyTextarea = $( '.wp-admin textarea' ),
 		lastScrollPosition = 0,
 		pinnedMenuTop = false,
 		pinnedMenuBottom = false,
@@ -327,6 +328,19 @@
 		$(e.target).parent().siblings('a').get(0).click();
 	});
 
+	// Adds a copy to clipboard button after a read-only textarea.
+	if ( adminReadonlyTextarea.is( '[readonly]' ) ) {
+		adminReadonlyTextarea.after( '<br><input type="button" value="Copy to Clipboard" class="button btn-copy-to-clipboard"/>' );
+
+		var copyButton   = $( '.btn-copy-to-clipboard' );
+
+		copyButton.on( 'click', function() {
+			var textareaSibling = $( this ).prev().prev();
+			textareaSibling.select();
+			document.execCommand( 'copy' );
+		})
+	}
+
 	$( '#collapse-button' ).on( 'click.collapse-menu', function() {
 		var viewportWidth = getViewportWidth() || 961;