Citizen Lab said Chinese and English-language versions of UC Browser, developed by UCWeb Inc, made easily available to third parties personally identifiable information like location, search details and mobile subscriber and device numbers.
               
The transmission of this information "represents a privacy risk for users because it allows anyone with access to the data traffic to identify users and their devices, and collect their private search data", it said in a report.
               
Alibaba spokesman Bob Christie said the problems were immediately fixed and customers notified of an update to the browser after Citizen Lab brought the issues to Alibaba's attention in April.
               
"We take security very seriously and we do everything possible to protect our users," he said.
               
Alibaba acquired UCWeb last June, in what was at the time the biggest merger in Chinese internet history.