Critical Sandbox Escape Flaw in Grist-Core Patched After Disclosure by Cyera Research Labs A high-severity sandbox escape vulnerability in Grist-Core, tracked as GHSA-7xvx-8pf2-pv5g (CVSS 9.1), has been patched following responsible disclosure by Cyera Research Labs. The flaw allowed attackers to achieve remote code execution (RCE) by exploiting malicious spreadsheet formulas that bypassed the platform’s Pyodide WebAssembly sandbox, exposing sensitive data and downstream systems. ### Vulnerability Details & Impact Grist-Core, a relational spreadsheet platform, is used by over 1,000 organizations, including France’s public sector educational institutions, to model business data, automate workflows, and integrate Python-based formulas. The platform operates in SaaS and self-hosted configurations, making it a critical data hub with access to customer records, operational metrics, and integration credentials. In SaaS deployments, a successful exploit could lead to RCE within the vendor’s control plane, potentially compromising multi-tenant workflows, credentials, and connected systems. ### Exploit Vectors & Patch Cyera Research Labs identified three distinct sandbox escape methods: 1. Python Class Hierarchy Traversal – Exploited `warnings.catch_warnings` to access full built-ins, enabling direct imports of the `os` module and command execution via `os.system()`. 2. Direct C Library Access – Leveraged `ctypes` to call `ctypes.CDLL(None).system()`, loading the `system()` function from libc via the Emscripten runtime. 3. Emscripten Runtime Manipulation – Used `emscripten_run_script_string()` to execute JavaScript in the host runtime, gaining access to `require('child_process')` and `process.env` for full host compromise. Grist released version 1.7.9 on January 20, 2026, addressing the issue by migrating Pyodide formula execution under Deno by default. This introduces a permission-based mediation layer, blocking sensitive operations unless explicitly granted. Organizations must ensure the `GRIST_PYODIDE_SKIP_DENO` flag is disabled, as enabling it reintroduces the vulnerability. The patch shifts Grist’s security model from a blocklist-based sandbox to a capability-based approach, significantly reducing the risk of formula-based exploitation.