opencost/opencost: technical due diligence, read from its repository

The median source file here is 129 lines. 16 files exceed 1,290 lines, the largest being 10,566. Size is not a defect on its own — some problems genuinely live in one place — but these are where merge conflicts, review fatigue and single-owner knowledge concentrate, and they are the first thing that slows an inheriting engineer down.

6 files were marked deprecated over two years ago and still are, the oldest since May 2023. A deprecation is a promise to remove. Ask what still depends on these, and whether removing them is scheduled.

The newest release, v2.5.3, is not on the branch this survey read; the newest release on it is v1.121.3. The shipped product may differ from what this report describes. Survey the release branch too.

Matches for AWS access key, Google API key, private key block were committed at some point across 3,337 commits examined. The files that held them are no longer in the working tree — but removal from a file is not removal from the history, and the history is what transfers with the asset. What matters is whether each was rotated after it was committed. The code cannot tell whether any of them is live, and that decides whether this matters: none sits in production configuration, and none is in a format its provider keeps for live keys. Is any of these live? Show that each was rotated after it was committed, and when. 1 other match set aside: expired tokens, licence tokens a vendor verifies with a public key, or placeholder text where a key would go. None grants access to anything.

18 third-party CI actions are referenced by a tag or branch rather than a commit, so they run whatever that tag points to on the day; 1 step pipes a download straight into a shell. Tags have been moved to malicious commits in real supply-chain attacks, and a piped script is whatever the server returns that minute. Pinning to a commit is the fix, and it is small.

3 of 320 locked dependencies match 5 published advisories in OSV, 1 of them rated high or critical. A lockfile says which version is installed, not whether the flawed code is reachable from this product, so each needs a look. Most are fixed by an upgrade, and the advisory names the version. This lockfile pins development tools alongside what ships and does not say which is which, so some of these may never reach a user.

The newest was published on 2026-07-30. A project that publishes advisories is telling its users about its fixes, and the count and pace say how much security work it carries. None of them affects the surveyed version.

Nothing in the service initialises an error reporter (Sentry, Rollbar, Bugsnag, Honeybadger or an APM agent). An exception in production reaches a person only if someone is reading the logs, which usually means a customer reports it first.