Users: Avoid defaulting new user's display name, nickname, or nicename to an email address

src/js/_enqueues/admin/user-profile.js

@@ -512,13 +512,17 @@
 		if ( select.length ) {
 			$('#first_name, #last_name, #nickname').on( 'blur.user_profile', function() {
 				var dub = [],
+					isEmail = $('#user_login').attr( 'data-is-email' ) === 'true',
 					inputs = {
 						display_nickname  : $('#nickname').val() || '',
-						display_username  : $('#user_login').val() || '',
 						display_firstname : $('#first_name').val() || '',
 						display_lastname  : $('#last_name').val() || ''
 					};
 
+				if ( ! isEmail ) {
+					inputs.display_username = $('#user_login').val() || '';
+				}
+
 				if ( inputs.display_firstname && inputs.display_lastname ) {
 					inputs.display_firstlast = inputs.display_firstname + ' ' + inputs.display_lastname;
 					inputs.display_lastfirst = inputs.display_lastname + ' ' + inputs.display_firstname;

src/wp-admin/includes/user.php

@@ -567,6 +567,56 @@ function default_password_nag() {
 	);
 }
 
+/**
+ * Computes the public display name options for the user profile screen.
+ *
+ * Excludes the user login from display options when the username is an email address,
+ * preventing email exposure in public author links, feeds, and bylines.
+ *
+ * @since 7.2.0
+ * @access private
+ *
+ * @param WP_User|int $user User object or user ID.
+ * @return string[] Array of unique display name choices.
+ */
+function _wp_get_user_profile_display_name_options( $user ) {
+	if ( ! $user instanceof WP_User ) {
+		$user = get_userdata( $user );
+	}
+
+	if ( ! $user ) {
+		return array();
+	}
+
+	$public_display                     = array();
+	$public_display['display_nickname'] = $user->nickname;
+
+	if ( ! is_email( $user->user_login ) ) {
+		$public_display['display_username'] = $user->user_login;
+	}
+
+	if ( ! empty( $user->first_name ) ) {
+		$public_display['display_firstname'] = $user->first_name;
+	}
+
+	if ( ! empty( $user->last_name ) ) {
+		$public_display['display_lastname'] = $user->last_name;
+	}
+
+	if ( ! empty( $user->first_name ) && ! empty( $user->last_name ) ) {
+		$public_display['display_firstlast'] = $user->first_name . ' ' . $user->last_name;
+		$public_display['display_lastfirst'] = $user->last_name . ' ' . $user->first_name;
+	}
+
+	if ( ! in_array( $user->display_name, $public_display, true ) ) {
+		$public_display = array( 'display_displayname' => $user->display_name ) + $public_display;
+	}
+
+	$public_display = array_map( 'trim', $public_display );
+
+	return array_values( array_unique( $public_display ) );
+}
+
 /**
  * Optional SSL preference that can be turned on by hooking to the 'personal_options' action.
  *

src/wp-admin/user-edit.php

@@ -472,7 +472,7 @@
 				<table class="form-table" role="presentation">
 					<tr class="user-user-login-wrap">
 						<th><label for="user_login"><?php _e( 'Username' ); ?></label></th>
-						<td><input type="text" name="user_login" id="user_login" aria-describedby="user-login-description" value="<?php echo esc_attr( $profile_user->user_login ); ?>" readonly="readonly" class="regular-text ltr" /> <span class="description" id="user-login-description"><?php _e( 'Usernames cannot be changed.' ); ?></span></td>
+						<td><input type="text" name="user_login" id="user_login" aria-describedby="user-login-description" value="<?php echo esc_attr( $profile_user->user_login ); ?>"<?php echo is_email( $profile_user->user_login ) ? ' data-is-email="true"' : ''; ?> readonly="readonly" class="regular-text ltr" /> <span class="description" id="user-login-description"><?php _e( 'Usernames cannot be changed.' ); ?></span></td>
 					</tr>
 
 					<?php if ( ! IS_PROFILE_PAGE && ! is_network_admin() && current_user_can( 'promote_user', $profile_user->ID ) ) : ?>
@@ -549,32 +549,9 @@
 						<td>
 							<select name="display_name" id="display_name">
 								<?php
-									$public_display                     = array();
-									$public_display['display_nickname'] = $profile_user->nickname;
-									$public_display['display_username'] = $profile_user->user_login;
-
-								if ( ! empty( $profile_user->first_name ) ) {
-									$public_display['display_firstname'] = $profile_user->first_name;
-								}
-
-								if ( ! empty( $profile_user->last_name ) ) {
-									$public_display['display_lastname'] = $profile_user->last_name;
-								}
-
-								if ( ! empty( $profile_user->first_name ) && ! empty( $profile_user->last_name ) ) {
-									$public_display['display_firstlast'] = $profile_user->first_name . ' ' . $profile_user->last_name;
-									$public_display['display_lastfirst'] = $profile_user->last_name . ' ' . $profile_user->first_name;
-								}
-
-								if ( ! in_array( $profile_user->display_name, $public_display, true ) ) { // Only add this if it isn't duplicated elsewhere.
-									$public_display = array( 'display_displayname' => $profile_user->display_name ) + $public_display;
-								}
-
-								$public_display = array_map( 'trim', $public_display );
-								$public_display = array_unique( $public_display );
-
-								?>
-								<?php foreach ( $public_display as $id => $item ) : ?>
+								$public_display = _wp_get_user_profile_display_name_options( $profile_user );
+								foreach ( $public_display as $item ) :
+									?>
 									<option <?php selected( $profile_user->display_name, $item ); ?>><?php echo esc_html( $item ); ?></option>
 								<?php endforeach; ?>
 							</select>

src/wp-includes/user.php

@@ -2198,6 +2198,8 @@ function validate_username( $username ) {
  * @since 5.3.0 The `user_activation_key` field can be passed to `$userdata`.
  * @since 5.3.0 The `spam` field can be passed to `$userdata` (Multisite only).
  * @since 5.9.0 The `meta_input` field can be passed to `$userdata` to allow addition of user meta data.
+ * @since 7.2.0 Default `display_name`, `nickname`, and `user_nicename` avoid using an email address
+ *              when `$user_login` is an email address.
  *
  * @global wpdb $wpdb WordPress database abstraction object.
  *
@@ -2208,13 +2210,15 @@ function validate_username( $username ) {
  *     @type string $user_pass            The plain-text user password for new users.
  *                                        Hashed password for existing users.
  *     @type string $user_login           The user's login username.
- *     @type string $user_nicename        The URL-friendly user name.
+ *     @type string $user_nicename        The URL-friendly user name. Default is a URL-safe version
+ *                                        of the user's login, or a generated slug (user-{random})
+ *                                        if the login is an email address.
  *     @type string $user_url             The user URL.
  *     @type string $user_email           The user email address.
- *     @type string $display_name         The user's display name.
- *                                        Default is the user's username.
- *     @type string $nickname             The user's nickname.
- *                                        Default is the user's username.
+ *     @type string $display_name         The user's display name. Default is the user's username,
+ *                                        or 'User {random}' if the username is an email address.
+ *     @type string $nickname             The user's nickname. Default is the user's username,
+ *                                        or 'User {random}' if the username is an email address.
  *     @type string $first_name           The user's first name. For new users, will be used
  *                                        to build the first part of the user's display name
  *                                        if `$display_name` is not specified.
@@ -2370,12 +2374,22 @@ function wp_insert_user( $userdata ) {
 		return new WP_Error( 'invalid_username', __( 'Sorry, that username is not allowed.' ) );
 	}
 
+	$email_login_suffix = '';
+	if ( is_email( $user_login ) ) {
+		$email_login_suffix = bin2hex( random_bytes( 4 ) );
+	}
+
 	/*
 	 * If a nicename is provided, remove unsafe user characters before using it.
-	 * Otherwise build a nicename from the user_login.
+	 * If updating an email-login user and no nicename is provided, preserve existing nicename.
+	 * Otherwise build a nicename from a random slug (if login is an email) or the user_login.
 	 */
 	if ( ! empty( $userdata['user_nicename'] ) ) {
 		$user_nicename = sanitize_user( $userdata['user_nicename'], true );
+	} elseif ( $update && is_email( $user_login ) && ! empty( $old_user_data->user_nicename ) ) {
+		$user_nicename = $old_user_data->user_nicename;
+	} elseif ( is_email( $user_login ) ) {
+		$user_nicename = 'user-' . $email_login_suffix;
 	} else {
 		$user_nicename = mb_substr( $user_login, 0, 50 );
 	}
@@ -2463,7 +2477,17 @@ function wp_insert_user( $userdata ) {
 	// Store values to save in user meta.
 	$meta = array();
 
-	$nickname = empty( $userdata['nickname'] ) ? $user_login : $userdata['nickname'];
+	if ( empty( $userdata['nickname'] ) ) {
+		if ( $update && is_email( $user_login ) && ! empty( $old_user_data->nickname ) ) {
+			$nickname = $old_user_data->nickname;
+		} elseif ( is_email( $user_login ) ) {
+			$nickname = 'User ' . $email_login_suffix;
+		} else {
+			$nickname = $user_login;
+		}
+	} else {
+		$nickname = $userdata['nickname'];
+	}
 
 	/**
 	 * Filters a user's nickname before the user is created or updated.
@@ -2498,7 +2522,13 @@ function wp_insert_user( $userdata ) {
 
 	if ( empty( $userdata['display_name'] ) ) {
 		if ( $update ) {
-			$display_name = $user_login;
+			if ( is_email( $user_login ) && ! empty( $old_user_data->display_name ) ) {
+				$display_name = $old_user_data->display_name;
+			} elseif ( is_email( $user_login ) ) {
+				$display_name = 'User ' . $email_login_suffix;
+			} else {
+				$display_name = $user_login;
+			}
 		} elseif ( $meta['first_name'] && $meta['last_name'] ) {
 			$display_name = sprintf(
 				/* translators: 1: User's first name, 2: Last name. */
@@ -2510,6 +2540,8 @@ function wp_insert_user( $userdata ) {
 			$display_name = $meta['first_name'];
 		} elseif ( $meta['last_name'] ) {
 			$display_name = $meta['last_name'];
+		} elseif ( is_email( $user_login ) ) {
+			$display_name = 'User ' . $email_login_suffix;
 		} else {
 			$display_name = $user_login;
 		}
@@ -2581,8 +2613,10 @@ function wp_insert_user( $userdata ) {
 	 *     @type string $user_pass       The user's password.
 	 *     @type string $user_email      The user's email.
 	 *     @type string $user_url        The user's url.
-	 *     @type string $user_nicename   The user's nice name. Defaults to a URL-safe version of user's login.
-	 *     @type string $display_name    The user's display name.
+	 *     @type string $user_nicename   The user's nice name. Defaults to a URL-safe version of user's login,
+	 *                                   or a generated slug (user-{random}) if the login is an email address.
+	 *     @type string $display_name    The user's display name. Defaults to the user's username, or
+	 *                                   'User {random}' if the username is an email address.
 	 *     @type string $user_registered MySQL timestamp describing the moment when the user registered. Defaults to
 	 *                                   the current UTC timestamp.
 	 * }