Reactive allows you to lock your store's XML feed. This option is typically used for Google & Facebook Shop XML files.
The reason for password protecting your XML is to now allow it's public access. Typically, you wouldn't want competitors to be able to see your product's stock and prices in a single file that is publicly accessible.
For that reason, Reactive strongly recommends that you use password protection for your Google & Facebook XML feeds. Unfortunately, Best Price & Skroutz doesn't allow such functionality.
To lock your feeds, scroll down to the Sales Channels page of your admin panel (Settings > Sales channels) and set a username and password.
Once you are done, save your changes.
The next step is to go to your Facebook & Google channels and choose "Lock XML Feed".
Once you perform those actions, your feeds will automatically have password protection enabled. Make sure to update your feed settings on Facebook & Google in order to avoid downtimes or errors to your XML feeds.