If you are banking with HDFC and have connected your Aadhaar account, here is a shocker.
As per HDFC's terms and conditions, the bank can share your aadhaar number with any third party without your consent.
From their T&Cs.
I give consent to the Bank to update my Aadhaar number in its records, basis information received by it through any external source/agencies, including government agencies. I also give consent to the Bank to disclose my Aadhaar number, as well as other related information, not restricted to the linked account number, to external institution(s) and/or regulatory body/bodies and/or statutory body/bodies and/or any other agent/s and/or vendor/s and/or contractors with whom the Bank enters, or has entered into any arrangement, in connection with providing of services / products.
Further, I agree that the Bank may use Aadhaar based transaction and/or authentication mechanism/system, either through biometric means or any other means deemed suitable by the Bank, as applicable and possible. (link)