Researcher says Bun's trusted install check can be bypassed through .bin links
X3r0Day says a rejected bin-linking report still yields install-time code execution on Bun 1.4.4 through a trusted package's postinstall script.
By Ryan Merket · Published
Primary source: x.com
Why it matters
Bun is Anthropic-owned infrastructure used to distribute and run Claude Code-era developer tooling. Its install-time trust boundary affects CI pipelines, scanners and automated updaters that install code without running the application. Bun says trustedDependencies was only ever about lifecycle scripts, while the PoC argues an untrusted bin entry placed on PATH delivers the install-time execution the gate was built to prevent.
Security researcher X3r0Day (@X3r0DaySec) said on November 6th that Bun rejected a reported install-time code execution issue as invalid, then shipped a change in Bun 1.4.4 for part of the behavior while leaving another variant working. In a thread on X, X3r0Day said Bun told the researcher that bin linking "has nothing to do with trustedDep" and was "not a bun issue." The researcher's public proof of concept, BunnyHijack-PoC, describes a gap in the trust boundary…
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