AmnesiaStealer Hijacks Logged-In Browser Sessions on macOS

Jamf Threat Labs published an analysis of AmnesiaStealer on 13 August after observing it in a ClickFix campaign. The lure imitated a GitHub download page, but instead of delivering legitimate software it instructed the visitor to open Terminal, paste a copied command and enter the device password.

That user action starts a multi-stage infection. The first script downloads and launches the Rust-based stealer; the malware then validates the requested Mac login password, gathers data and establishes persistence. A familiar-looking website and native password prompt do not make a command trustworthy.

Jamf found collection routines for macOS keychains, Chromium browser databases, Apple Notes, Telegram sessions and documents. The analysed malware also profiled the computer and its public-IP geolocation and contained a configurable cryptocurrency clipboard hijacker, although that function was disabled in the sampled build.

Some attempts to bypass Apple's privacy controls used older techniques that failed in Jamf's current macOS 26 testing. That limitation is useful, but it does not neutralise the rest of the stealer when a victim has deliberately run the command and supplied a password.

On command, AmnesiaStealer can download a second module that copies a Chromium profile and starts it in a hidden headless browser. Jamf says the operator can then control that browser interactively through the Chrome DevTools Protocol and export authenticated cookies in plaintext.

A stolen session can let an attacker act inside an account without first typing the password again. Multi-factor authentication remains important, but it may not stop abuse of a session that was already authenticated on the infected Mac.

Disconnect the Mac from the network and stop using it for email, banking, password management or crypto activity. From a separate trusted device, secure the primary email account first, change unique passwords, revoke active browser and app sessions, review multi-factor settings and watch financial or wallet accounts for unauthorised activity.

Because the malware can seek persistence and sensitive local data, deleting one downloaded file is not enough evidence that the system is clean. Preserve useful details for investigation and obtain qualified technical help to assess, erase and rebuild the Mac before restoring trusted data. Keep macOS and browsers current, but do not treat an update as cleanup after execution.

A VPN encrypts network traffic between the Mac and a VPN server and can replace the usual public IP address seen by many services. It does not inspect a shell command copied from a hostile page, prevent the user granting a password or stop malware reading data locally after execution.

It also cannot invalidate stolen cookies, revoke sessions or remove persistence. The defensive boundary here is endpoint trust: do not paste commands a website supplies, use trusted download routes, keep software updated and recover accounts from a clean device if compromise is suspected.

ClickFix succeeds by turning the victim into the installer. The instruction to paste a command should be treated as a security boundary, not as a clever workaround for a broken download. Legitimate software rarely needs a random website visitor to run an opaque Terminal command copied to the clipboard.

The hidden-browser stage also demonstrates why network encryption and account security are separate layers. A secure tunnel cannot protect a session once malicious code controls the endpoint on the trusted side of that tunnel.