I searched the WP 5.3.2 files on my computer and got these results.
wordpress/wp-includes/class-wp-customize-manager.php(4848): 'confirmDeleteTheme' => __( 'Are you sure you want to delete this theme?' ),
wordpress/wp-includes/class-wp-editor.php(1269): 'You have unsaved changes are you sure you want to navigate away?' =>
wordpress/wp-includes/functions.php(3137): * Display "Are You Sure" message to confirm the action being taken.
wordpress/wp-includes/functions.php(3140): * along with the "Are you sure?" message.
wordpress/wp-includes/pluggable.php(1098): * If the nonce value is invalid, the function will exit with an "Are You Sure?" style message.
wordpress/wp-includes/script-loader.php(1561): 'trashConfirm' => __( 'Are you sure you want to discard your unpublished changes?' ),
wordpress/wp-includes/script-loader.php(1650): 'warnQuickEdit' => __( "Are you sure you want to edit this comment?\nThe changes you made will be lost." ),
wordpress/wp-includes/script-loader.php(1651): 'warnCommentChanges' => __( "Are you sure you want to do this?\nThe comment changes you made will be lost." ),
wordpress/wp-includes/script-loader.php(1790): 'ays' => __( 'Are you sure you want to install this plugin?' ),
wordpress/wp-includes/script-loader.php(1874): 'aysDelete' => __( 'Are you sure you want to delete %s?' ),
wordpress/wp-includes/script-loader.php(1876): 'aysDeleteUninstall' => __( 'Are you sure you want to delete %s and its data?' ),
wordpress/wp-includes/script-loader.php(1877): 'aysBulkDelete' => __( 'Are you sure you want to delete the selected plugins and their data?' ),
wordpress/wp-includes/script-loader.php(1878): 'aysBulkDeleteThemes' => __( 'Caution: These themes may be active on other sites in the network. Are you sure you want to proceed?' ),
wordpress/wp-includes/wp-db.php(1104): $message .= '<li>' . __( 'Are you sure it exists?' ) . "</li>\n";
wordpress/wp-includes/wp-db.php(1691): $message .= '<li>' . __( 'Are you sure you have the correct username and password?' ) . "</li>\n";
wordpress/wp-includes/wp-db.php(1692): $message .= '<li>' . __( 'Are you sure you have typed the correct hostname?' ) . "</li>\n";
wordpress/wp-includes/wp-db.php(1693): $message .= '<li>' . __( 'Are you sure the database server is running?' ) . "</li>\n";
wordpress/wp-includes/wp-db.php(1850): $message .= '<li>' . __( 'Are you sure the database server is running?' ) . "</li>\n";
wordpress/wp-includes/wp-db.php(1851): $message .= '<li>' . __( 'Are you sure the database server is not under particularly heavy load?' ) . "</li>\n";
wordpress/wp-includes/js/tinymce/langs/wp-langs-en.js(294): newdocument: "Are you sure you want to clear all contents?",
wordpress/wp-includes/js/dist/editor.js(10381): alertMessage = Object(external_this_wp_i18n_["__"])('Are you sure you want to unpublish this post?');
wordpress/wp-includes/js/dist/editor.js(10383): alertMessage = Object(external_this_wp_i18n_["__"])('Are you sure you want to unschedule this post?');
wordpress/wp-includes/js/dist/editor.js(12641): var hasConfirmed = window.confirm(Object(external_this_wp_i18n_["__"])('Are you sure you want to delete this Reusable Block?\n\n' + 'It will be permanently removed from all posts and pages that use it.'));
wordpress/wp-admin/plugins.php(349): _e( 'Are you sure you want to delete these files and data?' );
wordpress/wp-admin/plugins.php(351): _e( 'Are you sure you want to delete these files?' );
wordpress/wp-admin/themes.php(167): 'confirmDelete' => __( "Are you sure you want to delete this theme?\n\nClick 'Cancel' to go back, 'OK' to confirm the delete." ),
wordpress/wp-admin/network/themes.php(149): <p><?php _e( 'Are you sure you want to delete this theme?' ); ?></p>
wordpress/wp-admin/network/themes.php(151): <p><?php _e( 'Are you sure you want to delete these themes?' ); ?></p>
wordpress/wp-admin/js/updates.js(1697): * opens an "Are you sure?" alert.