Actively exploited macOS 0day let hackers take screenshots of infected Macs

Gloved hands manipulate a laptop with a skull and crossbones on the display.

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Malicious hackers have been exploiting a vulnerability in fully updated versions of macOS that allowed them to take screenshots on infected Macs without having to get permission from victims first.

The zeroday was exploited by XCSSET, a piece of malware discovered by security firm Trend Micro last August. XCSSET used what at the time were two zerodays to infect Mac developers with malware that stole browser cookies and files; injected backdoors into websites; stole information from Skype, Telegram, and other installed apps; took screenshots; and encrypted files and showed a ransom note.

A third zeroday

Infections came in the form of malicious projects that the attacker wrote for Xcode, a tool that Apple makes available for free to developers writing apps for macOS or other Apple OSes. As soon as one of the XCSSET projects was opened and built, TrendMicro said, the malicious code would run on the developers’ Macs. An Xcode project is a repository for all the files, resources, and information needed to build an app.

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