Bottom line: Security researchers demonstrated manipulation of macOS apps through local package tampering without Gatekeeper blocking it, but Apple does not classify this as a security vulnerability.
Security researchers have demonstrated how macOS applications downloaded from internet sources can be manipulated without administrator rights. Apple does not assess this as a vulnerability because locally created app bundles fall outside the protection scope of Gatekeeper.
Researchers Talal Haj Bakry and Tommy Mysk showed a method by which core files of trusted macOS applications can be exchanged – such as Slack, Signal or the Brave browser. The prerequisite is that the respective app has been launched at least once after download and the attacker can already execute commands with user rights. Using tar commands, the app package can be archived, the original deleted, and the archive unpacked again. After this, macOS does not request new authentication when the main file is accessed again.
Following this manipulation, the modified application starts without Gatekeeper warnings. Although the exchanged program file does not assume the original permissions and digital signatures, there is a risk of misuse: if the manipulated app requests access to protected system areas such as the keychain, desktop, or documents, macOS displays the name and icon of the original, legitimate application. Users can thus be deceived into granting permission to malicious code.
Applications from the official Mac App Store are not affected by the method. These files are owned by the root system user and cannot be overwritten without elevated administrator rights. Apple reviewed the report and concluded that no security flaw exists. The company points out that Gatekeeper primarily inspects applications before first launch for known malware and modifications. Since the method demonstrated by the researchers does not directly modify the already signed executable file but rather creates a local app bundle, Apple sees no need for action. According to Apple’s assessment, locally created app bundles are not covered by macOS protection features – and exploiting permission prompts through social engineering is classified as outside the scope of impact.