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.cursor/rules/security.mdc

Cursor security rule for Unreal

A focused Cursor `.mdc` rule for auth, secrets, and untrusted input. It attaches when those files change, instead of repeating security policy in every chat. This copy is written for a Unreal project. This repository is an Unreal Engine project using C++. UObject memory is owned by the engine. Gameplay stays out of constructors that run before the world exists.

The example uses a balanced, readable style, pragmatic tests, and comments only where the intent is not obvious. Open the generator to make the agent stricter, switch to test-first, quiet the comments, or pick a different file.

The example assumes Unreal Engine with C++ gameplay code. It does not assume a particular networking model, Enhanced Input, or GAS unless the module already uses them.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: security.mdc

---
description: "Security rules for a Unreal repository"
globs: "**/*{auth,Auth,secret,config,Config}*"
alwaysApply: false
---

# Security rules

Attach these rules when editing auth, config, or secret-handling code in this Unreal repository.
This repository is an Unreal Engine project using C++. UObject memory is owned by the engine. Gameplay stays out of constructors that run before the world exists.

## Secrets and trust

- Do not trust client RPCs. Validate on the server.
- Do not ship private endpoints or keys in a cooked client.
- Sanitize any string that reaches a console command.

## Errors

- Fail at the boundary. Do not swallow errors.
- Use `ensure` or a logged early return for a missing asset. Do not check() on data a content change can break.

## Done when

- Untrusted input is validated before a side effect.
- No secret was added to source, logs, or a client bundle.
- The editor target compiles and the automation test or PIE session for the change was run.

Add it to the project

  1. 01

    Copy a starting file

    Copy the example Cursor security rule on this page, or open the generator if you want different testing, strictness, or comment rules.

  2. 02

    Save it at .cursor/rules/security.mdc

    Save it at `.cursor/rules/security.mdc` in the Unreal repo. Narrow the globs if your auth and config files live in a known folder.

  3. 03

    Start a fresh agent session

    Rules files are read when a session starts. A chat that is already open may still be using the old instructions.

  4. 04

    Give it one small task

    Ask for one change a Unreal agent often gets wrong, such as a UPROPERTY that is visible to the editor without a raw new of a UObject. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put Cursor security rule in a Unreal repo?

Save it at `.cursor/rules/security.mdc` in the Unreal repo. Narrow the globs if your auth and config files live in a known folder.

Which tools read this Cursor security rule?

Cursor loads `.cursor/rules/security.mdc` for files that match its globs. Pair it with the always-on project rule. It is not a substitute for code review.

What does the Unreal example assume?

The example assumes Unreal Engine with C++ gameplay code. It does not assume a particular networking model, Enhanced Input, or GAS unless the module already uses them.

Does VibeSpell upload my repository?

No. Recipe pages are static, and the generator builds the file in your browser from the options you pick. Your source code never leaves the machine.

Other files for Unreal

Cursor security rule for other stacks