Vulnerabilities exposing user data were found on hundreds of Android apps across multiple categories, potentially affecting the privacy of millions of users, ZDNet reported.

The bugs were reportedly uncovered by researchers at Columbia University in the US and related to improper use of cryptographic code, a set of algorithms designed to encipher data.

A total of 1,780 of the most popular apps in September in and October 2019 were examined, ZDNet stated, with problems found in 306. Some contained multiple bugs.

Only 18 app developers had responded to the research team after being approached, but none of the services were updated with bug fixes, the outlet wrote.

Another flaw, discovered in December 2019, let malware obtain user data including login credentials and location from 500 of the most popular Android apps.