FlutterShell Backdoor Spreads to macOS via Malicious Google and YouTube Ads

Cybersecurity researchers have shed light on a macOS malvertising campaign codenamed Operation FlutterBridge that spreads a new backdoor called FlutterShell. According to Palo Alto Networks Unit 42, the campaign is said to be the next stage of a previously reported activity cluster dubbed JSCoreRunner (aka FileRipple) in late August 2025.