cf is a local development tool. The web workbench binds to localhost and compiles and executes C++ that you type into it with your own user account; it is not designed to be exposed to untrusted users or the public internet. Within that model the following protections are in place:

• Compiler flags supplied from the browser are validated against an allowlist; flags that write files, add search paths, load plugins or pass through to the linker are rejected and reported (web/app/api/_engine/flags.ts).
• The /api/solution and /api/problem-text routes accept only a single safe path segment as the problem name, so requests cannot read or write outside the problems directory.
• Sources, stdin and captured output are size-capped, compilation and execution are time-limited, and every build runs in its own temporary directory.
• The problem store writes atomically and never evaluates stored content.

Do not run the workbench on a shared host or reverse-proxy it to the internet; the programs it runs are not sandboxed beyond the operating system's normal process isolation.

Only the latest release receives fixes.

Please do not open a public issue for a security problem. Use GitHub's private vulnerability reporting on this repository (Security -> Report a vulnerability) so the report stays confidential until a fix is available. Include the version (cf version or the Settings Server block), the platform, and steps to reproduce.

Reports are acknowledged within a few days, and a fix or mitigation is released as soon as one is ready.