Security

Overview

GptSkin changes how your Codex workspace looks, not how it works. This page explains exactly how the Skill applies themes, what it can and cannot touch, and the risks we believe you should know about. The Skill is open source on GitHub, so every claim here is auditable.

Loopback-Only CDP Injection

Themes are applied through the Chrome DevTools Protocol (CDP), enabled via a launch flag that binds the debugging port only to the loopback address (127.0.0.1). The injector pushes CSS variables, backgrounds, and controlled decorative layers into the running Codex app.

• The port is never exposed to your network — nothing off your machine can reach it.
• The Skill disconnects after applying the theme, but the loopback debugging port remains available for the lifetime of the Codex process launched with that flag.

What We Never Modify

GptSkin does not touch:

• The official app installation package or app.asar
• Code signatures
• Your API Key or Base URL
• Your Codex configuration files

Because nothing in the official installation is patched, an app update cannot be corrupted by GptSkin. Interface changes may require a Skill update or re-application.

No Access to Your Conversations

The injector does not read or modify your Codex conversation content. It does not transmit your Codex DOM, session data, or chat content to the cloud. The paid build service receives the image chosen for the theme and basic theme metadata — not the natural-language request used with Codex imagegen, and never your Codex session.

An Honest Disclosure: Loopback Port Risk

We want to be transparent about one inherent limitation: a loopback CDP port has no application-layer authentication. While the themed Codex process is running, another process under the same local user account could attempt to connect to that port. This requires code already running locally as you, but it is a real property of CDP. The Skill binds the port to 127.0.0.1, selects a Codex target, applies the theme, and disconnects promptly.

Theme Package Integrity

Theme packages delivered from our servers are verified with a hash check before application, so a corrupted or tampered package is rejected instead of being injected.

Credential Storage

Your gptskin.best API Key is stored in ~/.gptskin/config.json; the Skill creates the directory and file with restrictive permissions (0700 and 0600) on supported systems. The key is used only for authenticated Credit, upload, build, and theme retrieval requests.

Restore Mechanism

Every change GptSkin makes is reversible. Restore the default Codex theme removes all injected CSS, backgrounds, and decorative layers and restarts Codex normally — no leftovers, no repair installs.

Open Source and Auditable

The full Skill source is published at github.com/WendongAI/gptskin-skill. We encourage you to read the injector code, verify its Credit, image upload, build, and artifact requests, and confirm that it never reads your conversations. Found an issue? Report it to support@gptskin.best.