Paypal username and password for IPN

With paypal Website Payment Standard subscriptions.

Hi guys, I understand that username and password are generated after processed by Paypal side and we can also set IPN.

So can customers access subscription using that username and password and take action against the subscription that was purchased such as cancelling and upgrading?

I understand that passwords are hashed so how can we pass on to customers so the开发者_JS百科y can access this if they can login to paypal using those credentials?

Also when they actually do cancel or upgrade post-purchase, does IPN gets generated to notify automatically?

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No, these usernames and passwords are not used to access the subscriptions.
Only PayPal account holders can sign up for subscriptions by default with Website Payments Standard. They can review / cancel these subscriptions through 'My pre-approved payments' in the PayPal account.
You, as a merchant, can review them through 'Recurring payments dashboard'.

You can start accepting subscription signups from non-PayPal account holders by signing up for Enhanced Recurring Payments (available in US/UK only).
However, only you will be able to review / cancel existing subscriptions. The username / password is, as said, not used for controlling the subscription. They are merely created for your benefit so you can have a 1:1 subscription:username connection to integrate into your website's access control (e.g. .htaccess)