A pull request added a dependency that an AI assistant had suggested. The package name did not exist when the code was written, and a few weeks later someone else published it. We caught it in review by luck, then added registry checks so we do not rely on luck.
An internal audit found a workflow that used pull_request_target to post preview links and also checked out the pull request's code and ran npm install. Any fork PR could have run code with our deploy token. We split it into an unprivileged build and a privileged comment step.
In March 2025 the popular tj-actions/changed-files action was compromised and its version tags were repointed to code that printed CI secrets into workflow logs. Three of our repositories used it by tag. This is how we checked exposure, rotated secrets and moved to SHA pinning.