Using just subscribers’ mobile numbers, a flaw in Airtel’s mobile app could have been exploited to access subscribers’ sensitive information, including their email, address and device IMEI number, BBC reported. This put the privacy of more than 300 million subscribers in jeopardy. Other information about a subscriber that could have been accessed (ab)using the flaw were users’ name, gender, date of birth, address, subscription information, device capability information for 4G, 3G, GPRS, network information, activation date and user type (prepaid/postpaid). The flaw was discovered by independent security researcher Ehraz Ahmed.

Airtel told BBC that the flaw has since been fixed. When contacted, Airtel sent us the following statement:

“There was a technical issue in one of our testing APIs, which was addressed as soon as it was brought to our notice. Since these were testing APIs, we can now confirm that no data related to our customers has been impacted. 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.”

Ahmed told MediaNama, “I usually look for high-risk vulnerabilities in applications that store vast amounts of data, Luckily, I found this in Airtel, and got it fixed before it being exploited.” However, he told us that he wasn’t entirely sure if the flaw had indeed not been exploited before he discovered it, and said that it took him 15 minutes to find the flaw. He discovered the flaw on November 29, and the BBC reported on it on December 7. This means that the flaw was present in the Airtel app for more than a week.

This incident comes at a time when India still doesn’t have a privacy law. India’s Personal Data Protection Bill, 2019, which got the Union Cabinet approval on December 4, is yet to be tabled in Parliament.

In November, a flaw in the API of caller-ID app Truecaller, allowed hackers to use malicious links to harvest IP addresses, physical location, and other data of users by attacking them using brute force and distributed denial of service (DDoS). Before that, in July, a “bug” in the Truecaller app started registering users to the app’s UPI platform without them necessarily consenting to it.

*Update: This post was updated with Airtel’s response to our queries, and with the date on which Ahmed discovered the flaw. The previous version of this story has been archived here.