Index: src/wp-admin/includes/class-wp-plugin-install-list-table.php
===================================================================
--- src/wp-admin/includes/class-wp-plugin-install-list-table.php	(revision 36916)
+++ src/wp-admin/includes/class-wp-plugin-install-list-table.php	(working copy)
@@ -467,7 +467,20 @@
 						break;
 					case 'latest_installed':
 					case 'newer_installed':
-						$action_links[] = '<span class="button button-disabled">' . _x( 'Installed', 'plugin' ) . '</span>';
+						$plugins = get_plugins( '/' . $plugin['slug'] );
+						$plugin_file = '';
+
+						if ( ! empty( $plugins ) ) {
+							$plugin_file = $plugin['slug'] . '/' . key( $plugins );
+						}
+
+						if ( $plugin_file && ! is_plugin_active( $plugin_file ) ) {
+
+							$activate_url = wp_nonce_url( 'plugins.php?action=activate&amp;plugin=' . $plugin_file, 'activate-plugin_' . $plugin_file );
+							$action_links[] = sprintf( '<a class="button" href="%s" title="%s" target="_parent">%s</a>', esc_url( $activate_url ), esc_attr__( 'Activate this plugin' ), _x( 'Activate', 'plugin' ) );
+						} else {
+							$action_links[] = sprintf( '<span class="button button-disabled" title="%s">%s</span>', esc_attr__( 'This plugin is already installed and is up to date' ), _x( 'Installed', 'plugin' ) );
+						}
 						break;
 				}
 			}