If a Taobao seller leaks buyer information, you should immediately report the matter to the Taobao customer service. The specific steps are as follows:

1. Log in to your Taobao account, find the "Customer Service" button in the upper right corner of the page, and click it to enter the customer service page.

2. On the customer service page, find the "Help Center" column, select the "Complaints and Rights Protection" option in the "Knowledge Base" to enter the relevant page.

3. On the "Complaints and Rights Protection" page, select "Buyer Rights Protection" - "Rights Protection Record Query" - "I Want to Report" to make a complaint.

4. Fill in the necessary reporting information according to the page prompts, including the name of the Taobao seller's store that leaked the information, the specific information leaked, and the reporter's contact information.

5. After submitting the reporting information, Taobao customer service will investigate and handle the matter, and impose corresponding penalties and compensation on the seller according to the circumstances.

At the same time, buyers can also contact Taobao customer service or relevant departments to file complaints and keep relevant evidence and records for future use in case of problems.