FulcrumSec Claims Arup Breach Exposed GitHub Repos, Cloud Data, and Client Projects

FulcrumSec has claimed responsibility for breaching UK engineering firm Arup Group and stealing large volumes of data, later listing the company on its Tor leak site. According to the threat actor’s account, the intrusion began in September 2025 after attackers found a GitHub personal access token hardcoded in a JavaScript file on a forgotten Arup subdomain, which allegedly opened access to more than 10,000 private repositories and led to additional credentials in code. The group said it exfiltrated about 700GB of GitHub repositories, 2TB of Azure and AWS S3 data, database backups, source code, and other internal material before credentials were rotated.

The stolen data allegedly included sensitive information tied to major clients and infrastructure projects, including HS2-related repositories, Euston Station design files, archaeological GPS coordinates, Neuron BMS and Odoo ERP data, Apple code-signing certificates with plaintext passwords, and GCP payment gateway credentials. FulcrumSec said Arup detected parts of the intrusion roughly six weeks after initial access but that the attackers retained visibility into the environment for months, analyzing the haul before contacting the company in April 2026. The incident underscores the downstream risk posed by hardcoded secrets, forgotten internet-facing assets, delayed credential rotation, and weak monitoring of source-code and cloud environments.