Also experiencing the exact same problem. Any news?
Disabling doesn’t always work immediately btw — cache etc. needs to refresh I presume. Mine took a couple of minutes to start working again.
You try just renaming the plugin folder with the suffix “-disabled” ?
Same problem — from the same update!
I suggest you disable the plugin as a temporary measure but this is the offending code:
$requested_temp_dir = sanitize_text_field($_GET['wp_db_temp_dir']);
$this->backup_dir = trailingslashit(apply_filters('wp_db_b_backup_dir', (isset($requested_temp_dir) && is_writable($requested_temp_dir)) ? $requested_temp_dir : get_temp_dir()));
$this->basename = 'wp-db-backup';
