For years the Cydia Store was a key component of the iPhone jailbreak scene — jailbreaking an iPhone or iPad gives you access to files, settings, and features that would otherwise be unavailable, but the Cydia Store makes it easy to find and install apps that take advantage of those features.
To be clear — users can still download free apps from Cydia, and folks who’ve already paid for apps/tweaks can continue to download them.
What’s gone is the ability to pay for items in the Cydia Store. That’s due to a vulnerability that opened the door for malware to cause logged-in-users to make unauthorized purchases using PayPal. No user data was compromised, but it was still a pretty serious bug — and a complicated one to fix. The person who discovered the bug recommends users unlink their PayPal accounts from the Cydia Store.
Saurik says one reason he had been planning to shut down the Cydia Store by the end of 2018 was that it was difficult and expensive to maintain, and didn’t bring in even enough revenue to cover the store’s hosting fees — he’s currently paying for the costs of serving “many terabytes of bandwidth per month” out of his own pocket.