XCSSET Mac Malware: Infects Xcode Projects, Performs UXSS Attack on Safari, Other Browsers, Leverages Zero-day Exploits

Trend Micro has discovered an unusual infection related to Xcode developer projects. Upon further investigation, we discovered that a developer’s Xcode project at large contained the source malware, which leads to a rabbit hole of malicious payloads. Most notable in our investigation is the discovery of two zero-day exploits: one is used to steal cookies via a flaw in the behavior of Data Vaults, another is used to abuse the development version of Safari.

This scenario is quite unusual; in this case, malicious code is injected into local Xcode projects so that when the project is built, the malicious code is run. This poses a risk for Xcode developers in particular. The threat escalates since we have identified affected developers who shared their projects on GitHub, leading to a supply-chain-like attack for users who rely on these repositories as dependencies in their own projects. We have also identified this threat in sources such as VirusTotal, which indicates this threat is at large.

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Source: Trend Micro