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Zero-Day Flaws Found in Dolphin, Mercury Browsers for Android

A researcher has advised customers of the Dolphin and Mercury web browsers for Android to switch to other applications after identifying a series of zero-day vulnerabilities that put users at risk.

A researcher has advised customers of the Dolphin and Mercury web browsers for Android to switch to other applications after identifying a series of zero-day vulnerabilities that put users at risk.

Information from Google Play shows that Dolphin Browser for Android has between 50 million and 100 million installs, while Mercury Browser for Android has between 500,000 and 1 million installs.

A mobile security researcher known online as “rotlogix” has analyzed the popular browsers. According to the expert, the Dolphin browser is plagued by a vulnerability that can be exploited by a man-in-the-middle (MitM) attacker for arbitrary file writing and even remote code execution. The researcher says Dolphin developers have been made aware of the security hole.

The flaw is related to a feature that allows users to download and apply themes for the web browser. Because the themes are downloaded over HTTP, an MitM attacker can inject a specially crafted file.

Rotlogix has demonstrated that a malicious actor could create a theme file that can modify an existing Dolphin library that is loaded at startup ( in order to execute arbitrary code.

“Through the exploitation of this functionality, an attacker can achieve an arbitrary file write, which can then be turned into code execution within the context of the browser on the user’s device,” the researcher explained in a blog post published over the weekend. “The only user interaction this requires is selecting, downloading, and applying a new Dolphin Browser theme.”

Mercury Browser for Android users are exposed to attacks due to a couple of unpatched vulnerabilities that can be combined by a remote attacker to read and write arbitrary files within the application’s data directory.

“The Mercury Browser for Android suffers from an insecure Intent URI scheme implementation and a path traversal vulnerability within a custom web server used to support its WiFi Transfer feature,” the expert said.

A remote attacker can exploit the vulnerabilities by getting the victim to open a specially crafted HTML page.

Earlier this year, the researcher identified a similar insecure intent URI implementation flaw in Mercury Browser for Android. He also discovered that the password users could set to protect Mercury, and OAuth tokens for Box file sharing accounts had been stored insecurely.

Since these vulnerabilities have not been fixed, Rotlogix advises Android users to utilize other web browsers. The developers of the Dolphin and Mercury browsers have not responded to SecurityWeek’s request for comment.

Written By

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.

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