Security Experts:

Bug Exposed Direct Messages of Millions of Twitter Users

Millions of Twitter Users Affected by Information Exposure Flaw

Twitter has patched a bug that may have caused direct messages to be sent to third-party developers other than the ones users interacted with. The problem existed for well over a year and it impacted millions of users.

According to Twitter, the issue is related to the Account Activity API (AAAPI), which allows developers registered on the social network’s developer program to build tools designed to better support businesses and their customer communications on the platform.

Users who between May 2017 and September 10, 2018, interacted with an account or business on Twitter that relied on a developer using the AAAPI may have had their messages sent to a different registered developer.Information Exposure Vulnerability Affected Millions of Twitter Users

“In some cases this may have included certain Direct Messages or protected Tweets, for example a Direct Message with an airline that had authorized an AAAPI developer. Similarly, if your business authorized a developer using the AAAPI to access your account, the bug may have impacted your activity data in error,” Twitter said.

Twitter determined that less than 1% of users are impacted, but that still represents roughly 3 million accounts – Twitter reported having 335 million active users in the second quarter of 2018. Affected users are being notified by the company, which has also reached out to developers who may have received messages in error to ensure that the information is deleted.

While this may seem like a serious issue, Twitter claims that a specific set of technical circumstances are required to trigger the bug. This includes two or more registered developers having AAAPI subscriptions for domains on the same public IP, matching URL paths (e.g. example.com/[webhooks/twitter] andanotherexample.com/[webhooks/twitter), activity from both devs within the same 6-minute timeframe, and subscriber activity originating from the same Twitter backend server.

“Our team has been working diligently with our most active enterprise data customers and partners who have access to this API to evaluate if they were impacted. Through our work so far, and the information made available to us by our partners, we can confirm that the bug did not affect any of the partners or customers with whom we have completed our review,” Twitter said on Friday.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.