I got this error after installing a third-party free theme. Full text of the error:
Warning: sprintf(): Too few arguments in /wp-admin/includes/class-bulk-upgrader-skin.php on line 152
Here is the solution – in the file /wp-admin/includes/class-bulk-upgrader-skin.php find and replace this code:
if ( $this->result && ! is_wp_error( $this->result ) ) { if ( ! $this->error ) { echo '<div class="updated js-update-details" data-update-details="progress-' . esc_attr( $this->upgrader->update_current ) . '">' . '<p>' . sprintf( $this->upgrader->strings['skin_update_successful'], $title ) . ' <button type="button" class="hide-if-no-js button-link js-update-details-toggle" aria-expanded="false">' . __( 'Show details.' ) . '</button>' . '</p></div>'; } echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js($this->upgrader->update_current) . '\').hide();</script>'; }
to this one:
if ( $this->result && ! is_wp_error( $this->result ) ) { if ( ! $this->error ) echo '<div class="updated"><p>' . sprintf($this->upgrader->strings['skin_update_successful'], $title, 'jQuery(\'#progress-' . esc_js($this->upgrader->update_current) . '\').toggle();jQuery(\'span\', this).toggle(); return false;') . '</p></div>'; echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js($this->upgrader->update_current) . '\').hide();</script>'; }