Security for OSS Maintainers: A Survival Guide for Library Authors

Maintaining open source software (OSS) is a thankless job. You write code for free, and when it breaks, people yell at you.

When it has a security vulnerability (like React2Shell), they don't just yell—they panic.

If you maintain a library used by others, you are part of the software supply chain. Here is your survival guide to keeping your package—and your reputation—intact.

1. Define Your Trust Boundaries

The #1 mistake library authors make is not defining who is allowed to provide what data.

• Does your library parse input?
• Does it accept configuration objects?
• Does it execute callbacks?

Rule: If your library accepts an object that controls logic (like a config with function callbacks), document loudly that this input must not come from user data.

2. Fuzz Testing

Unit tests check the happy path. Fuzz tests check the chaotic path.

Fuzzing involves throwing random, malformed garbage at your functions to see if they crash or behave unexpectedly.

• Tools: fast-check (JS), AFL (C/C++).
• Goal: Find edge cases where your parser enters an infinite loop or exposes internal state.

// Example: fast-check property based testing
import fc from 'fast-check';

test('myParser never crashes', () => {
  fc.assert(
    fc.property(fc.string(), (input) => {
      try {
        parse(input);
        return true;
      } catch (e) {
        return true; // Crashing gracefully is fine. RCE is not.
      }
    })
  );
});

3. Handling Vulnerability Reports

Someday, you will get an email: "I found a vulnerability in your package."

DO NOT:

• Ignore it.
• Reply angrily.
• Fix it silently without a CVE.

DO:

1. Acknowledge: "Received. We are investigating."
2. Verify: Reproduce the exploit in a private environment.
3. Patch: Create a fix.
4. Coordinate: Ask the reporter for a targeted disclosure date.
5. Publish: Release the patch + Security Advisory (GitHub Security Advisories are great for this).

4. Supply Chain Attacks

Sometimes the vulnerability isn't in your code, but in your dependencies.

• Lock your dependencies: Use package-lock.json or pnpm-lock.yaml.
• Pin versions: Avoid ^ ranges for critical internal deps if you can manage the update toil.
• 2FA: Enable Two-Factor Authentication on npm. Do it now.

Conclusion

You don't have to be a security expert to be a safe maintainer. You just have to be defensive. Assume every input is a weapon until proven otherwise.