Securing Local Configuration Directories for AI Coding Assistants

1. The Overlooked Risk: A “Time Bomb” in the Local Configuration Directory

When deeply configuring the local configuration directory of an AI coding assistant, most developers focus on project memory files used to constrain model behavior and on custom skills. However, they often overlook a small but highly sensitive local settings file.

This file is commonly named something like settings.local.json and stores “personal-level” configuration. One of the most dangerous items in this file is the allow list. Once credentials are mixed into this list, the repository can become a ticking time bomb.

A public code audit illustrated this risk: researchers scanned public code hosting platforms and found that at least thousands of such local settings files contained at least one secret. This is not an isolated case, but a systematic configuration flaw.

2. How Secrets End Up in the File

To understand the problem, first understand why this file gets secrets written into it.

When an AI coding assistant needs to execute a command, such as connecting to a database or fetching a private resource, it usually shows a confirmation prompt. To save time, developers often choose the option similar to “allow this time and do not ask again.” At this point, a “helpful” behavior of the tool — writing the entire command text into an allow rule — becomes the source of the leak:

{
  "permissions": {
    "allow": [
      "psql postgresql://admin:S3cr3tP@ss@db.internal:5432/prod"
    ]
  }
}

The command contains a plaintext password, but the tool stores it verbatim in the local settings file. The developer thinks they have only “allowed one operation,” but in reality they have “hung a key at the front door.”

The core problem is not that the tool “remembers commands.” The problem is that it persists commands and credentials together without redacting sensitive fragments or replacing them with variables.

3. Why Global Git Exclude Rules Cannot Save You

Some developers may ask: Does the tool automatically exclude this kind of file?

In many AI coding assistants, when the local settings file is first written, it is appended to the current user’s machine-level global Git exclude, such as ~/.config/git/ignore. But this is an easily misunderstood “security illusion”:

• A global exclude belongs to machine-level configuration and is not distributed with the repository.
• When someone clones your repository, they do not receive your local exclude rules.
• If you switch to another computer or reconfigure the environment, the exclude rules are also lost.
• If the file is created by the tool after git init and the rule was not in effect at that time, it may be included in version control normally.

In other words, this protection is “best-effort,” machine-bound, and non-transferable. Once the file is added with git add and committed, it truly enters the repository history. In one repository that was scanned, the file had already been present for more than 200 days. More interestingly, in more than half of the scanned repositories, the commit that modified the file still listed the AI assistant as a co-author. This means the leak often happens during normal human-machine collaboration, not through malicious behavior.

4. The Real Scale of the Problem

When scattered cases are combined, the situation is serious. The audit identified thousands of distinct secrets in public repositories. Database passwords alone were close to four hundred. The findings also included:

• SSH private keys or passphrases;
• Cloud provider access keys, such as Access Key / Secret Key types;
• High-privilege keys from third-party data storage platforms, such as service-role keys, which can often bypass row-level permissions.

Once high-privilege keys leak, attackers can directly read and write production data or move laterally. The impact is far greater than a single application being compromised.

5. Deleting the File Is Not Enough

After discovering a leak, the most common wrong reaction is “delete the file and commit a fix.” This treats the symptom but not the root cause:

1. Git history still exists: If the file was ever committed, its snapshot remains in historical commits. Anyone can retrieve the old version with git log or git show.
2. Forks and clones have already spread: Once a repository is forked or cloned, the secret has already been copied into copies you cannot control.
3. Caches and mirrors: Code search engines and mirror sites may already have indexed historical versions containing the secret.

Therefore, deletion can only stop the bleeding at the latest commit. It cannot retroactively remove credentials that have already leaked.

6. The Correct Way to Configure Local Settings

The truly secure approach is to completely separate “credential management” from the “command allow list.” The following practices are actionable.

1. Rotate First, Then Clean Up (the order matters)

Since the secret may already have leaked, the first step is always to invalidate the old credential:

• Immediately rotate all passwords, tokens, and keys that may have appeared or are suspected to have appeared in the configuration file;
• Change database passwords, reissue cloud keys, regenerate SSH key pairs, and revoke old public keys;
• Do not rush to clean the repository before rotation is complete, to avoid delaying incident response because of the belief that “deleting it is enough.”

2. Stop Tracking the File in Version Control

For sensitive configuration files that have already been committed:

# Stop tracking but keep the local file
git rm --cached path/to/settings.local.json
# Commit this change
git commit -m "stop tracking local settings file"

If the history already contains secrets, the team should evaluate whether to use a history rewriting tool to remove them completely, and notify all collaborators to clone again.

3. Use the Repository’s Own .gitignore, Not a Global Exclude

Do not rely on machine-bound global exclude rules. Put ignore rules in the project-level .gitignore file, which is distributed with the repository:

# Personal local settings must not enter version control
settings.local.json
*.local.json
.env
.env.*

This gives every cloner consistent protection.

4. Use Variable Placeholders in Commands and Avoid Plaintext

Never put plaintext credentials into commands that may enter configuration files or Git history. Use environment variable injection instead:

# Bad example: plaintext password enters the command and configuration
psql postgresql://admin:S3cr3tP@ss@db.internal/prod
# Good example: credentials are injected by environment, and only variable names appear in the command
psql "$DB_URL"

Sensitive values should be stored in controlled secret management facilities or in .env, and .env must be ignored. They should be injected at runtime through environment variables.

5. Authorize Command Patterns, Not Entire Commands

When configuring allow rules, try to authorize reusable, non-sensitive command patterns rather than a specific command with parameters:

{
  "permissions": {
    "allow": [
      "script:run:*",
      "make build",
      "git status"
    ]
  }
}

Pattern-based authorization such as “run a certain type of script” or “execute a build” preserves convenience while preventing credentials carried in a specific invocation from becoming fixed in configuration. The principle is: grant capabilities, not specific secret-bearing commands.

6. Perform Regular Checks

• Integrate secret scanning into CI to block commits in real time;
• Regularly review whether the local configuration directory is consistent with .gitignore;
• For high-privilege keys, such as service-role keys, prioritize switching to least-privilege credentials to reduce the blast radius.

7. Summary

The local configuration directory is dangerous because it sits at the intersection of “human-machine collaboration convenience” and “credential security.” One click on “do not ask again” can freeze a secret into version control.

The correct approach to deep configuration is not to focus on how much the tool remembers, but to ensure that:

• credentials never enter command text,
• command text never enters version control,
• and version control never leaks high-privilege keys.

The implementation order is: rotate and stop the bleeding → stop tracking → project-level ignore → variable injection → pattern-based authorization → continuous scanning. Turning this workflow into a team standard is the real way to protect this often-overlooked line of defense.