According to the cyber security researcher Ehraz Ahmed the flaw existed in one of the Airtel app that allows "to fetch sensitive user information of any Airtel subscriber."
"It revealed information like first and last name, gender, email, date of birth, address, subscription information, device capability information for 4G, 3G & GPRS, network information, activation date, user type (prepaid or postpaid) And current IMEI number," Ahmed said in his blog.
The IMEI number is a unique number that can be used to identify the device of the user.
"Every user that is on India's Airtel network was at risk of getting his information leaked through this vulnerability, and risking over 325.5 million subscribers in India," Ahmed said.
When contacted Bharti Airtel spokesperson acknowledged the flaw and said that it has been fixed as soon as the company was alerted about it.
"There was a technical issue in one of our testing APIs, which was addressed as soon as it was brought to our notice. Airtel's digital platforms are highly secure. Customer privacy is of paramount importance to us and we deploy the best of solutions to ensure the security of our digital platforms," Airtel spokesperson said. PRS RCJ