A critical flaw has been discovered in WhatsApp’s “View Once” feature, a tool designed to enhance privacy by allowing users to send photos and videos that disappear after being viewed once. Researchers from Zengo X uncovered this vulnerability, revealing that attackers are actively exploiting the flaw to save and distribute media without the sender’s knowledge or consent. This undermines the feature’s intended purpose, which is to offer a more secure way to share sensitive content.
The core issue lies in WhatsApp’s handling of “View Once” media. These messages are essentially regular media files with a “View Once” flag that determines whether they disappear after being viewed. Attackers can modify this flag, changing it from “true” to “false,” effectively converting the media into a regular, downloadable message. Furthermore, WhatsApp’s system sends the media to all linked devices, including web applications, making it easier for attackers to intercept and manipulate the content.
Researchers also noted that some versions of “View Once” messages contain low-quality previews, which can be viewed without downloading the full media. Moreover, media files are not deleted from WhatsApp’s servers immediately after being downloaded, remaining accessible for up to two weeks. This increases the window of opportunity for attackers to exploit the flaw. The vulnerability is not just theoretical—cybercriminals have already developed modified WhatsApp Android apps and web extensions that automate the process of bypassing the “View Once” restriction.
To address this issue, WhatsApp may need to implement a more robust Digital Rights Management (DRM) system that verifies hardware support for privacy controls. Alternatively, limiting “View Once” media to the primary mobile device rather than sending it to all linked devices could mitigate the risk. Until a solution is found, users should be cautious when sharing sensitive content through the “View Once” feature, as it may not provide the level of privacy they expect.
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