Blockchain.info has a service to list all the transactions which involve a bitcoin addresses generated using a given xpub.How does this work? As per my understanding, there could be infinite addresses which can be generated, so how does this work?

Link: https://blockchain.info/xpub/xpub6CUGRUonZSQ4TWtTMmzXdrXDtypWKiKrhko4egpiMZbpiaQL2jkwSB1icqYh2cfDfVxdx4df189oLKnC5fSwqPfgyP3hooxujYzAu3fDVmz
BIP-44 specifies a limit to how a wallet should look for public keys. The implementation should consider there's no address with funds beyond 20 addresses without funds.