Index: src/wp-signup.php
===================================================================
--- src/wp-signup.php	(revision 41144)
+++ src/wp-signup.php	(working copy)
@@ -114,7 +114,7 @@
 	if ( !is_subdomain_install() )
 		echo '<span class="prefix_address">' . $current_network->domain . $current_network->path . '</span><input name="blogname" type="text" id="blogname" value="'. esc_attr($blogname) .'" maxlength="60" /><br />';
 	else
-		echo '<input name="blogname" type="text" id="blogname" value="'.esc_attr($blogname).'" maxlength="60" /><span class="suffix_address">.' . ( $site_domain = preg_replace( '|^www\.|', '', $current_network->domain ) ) . '</span><br />';
+		echo '<input name="blogname" type="text" id="blogname" value="'.esc_attr($blogname).'" maxlength="60" autocomplete="off" /><span class="suffix_address">.' . ( $site_domain = preg_replace( '|^www\.|', '', $current_network->domain ) ) . '</span><br />';
 
 	if ( ! is_user_logged_in() ) {
 		if ( ! is_subdomain_install() ) {
@@ -229,7 +229,7 @@
 	if ( $errmsg = $errors->get_error_message('user_name') ) {
 		echo '<p class="error">'.$errmsg.'</p>';
 	}
-	echo '<input name="user_name" type="text" id="user_name" value="'. esc_attr( $user_name ) .'" autocapitalize="none" autocorrect="off" maxlength="60" /><br />';
+	echo '<input name="user_name" type="text" id="user_name" value="'. esc_attr( $user_name ) .'" autocapitalize="none" autocorrect="off" maxlength="60" autocomplete="off" /><br />';
 	_e( '(Must be at least 4 characters, letters and numbers only.)' );
 	?>
 
Index: src/wp-includes/general-template.php
===================================================================
--- src/wp-includes/general-template.php	(revision 41144)
+++ src/wp-includes/general-template.php	(working copy)
@@ -460,7 +460,7 @@
 			' . $login_form_top . '
 			<p class="login-username">
 				<label for="' . esc_attr( $args['id_username'] ) . '">' . esc_html( $args['label_username'] ) . '</label>
-				<input type="text" name="log" id="' . esc_attr( $args['id_username'] ) . '" class="input" value="' . esc_attr( $args['value_username'] ) . '" size="20" />
+				<input type="text" name="log" id="' . esc_attr( $args['id_username'] ) . '" class="input" value="' . esc_attr( $args['value_username'] ) . '" size="20" autocomplete="off" />
 			</p>
 			<p class="login-password">
 				<label for="' . esc_attr( $args['id_password'] ) . '">' . esc_html( $args['label_password'] ) . '</label>