Noma's research team demonstrates that GitHub's Copilot coding agent can be weaponized purely by planting a poisoned issue in a public repo — no stolen credentials or zero-days required. They frame this as a textbook indirect prompt injection where the agent conflates adversarial repo content with the user's task, then exfiltrates private code through legitimate agent-authorized channels like commits or comments.
By submitting the Noma writeup to Hacker News and driving it to 213 points, ColinEberhardt is signal-boosting the position that this is a serious, credible demonstration worth the developer community's attention. The strong upvote count suggests broad agreement that this moves prompt injection from theoretical risk to concrete production vulnerability.
The editorial argues GitLost isn't a GitHub-specific failure but a structural property of every coding agent on the market — Copilot, Cursor background agents, Devin, and Claude Code in autonomous mode all read untrusted content and act with the user's privileges. As long as agents can't distinguish task instructions from adversarial repo content, the vulnerability class persists regardless of vendor.
Noma highlights that the exfiltration happens through actions the Copilot agent is explicitly authorized to perform — commits, comments, outbound fetches — meaning the audit log shows nothing anomalous. This inverts the usual security assumption that logging and identity scoping provide defense in depth; here they provide cover for the attacker.
Researchers at Noma Security published a proof-of-concept they're calling GitLost, showing how GitHub's Copilot coding agent — the autonomous variant that can be assigned issues, open branches, and file pull requests on your behalf — could be tricked into exfiltrating code from private repositories it had legitimate access to. The attacker never needed a zero-day, a stolen token, or a compromised maintainer account. They only needed the agent to read an issue.
The exploit is a textbook indirect prompt injection: a poisoned issue in a public repo contains hidden instructions that the Copilot agent dutifully treats as part of its task. Once the agent picks up the assignment, those instructions redirect it to enumerate other repositories the underlying identity can see — including private ones — and encode chunks of that source into an outbound request the agent is allowed to make (a commit, a comment, a fetched URL). The private code ends up somewhere the attacker controls, all while the audit log shows the agent doing exactly what an agent is supposed to do.
Noma's writeup walks through the mechanics: the agent runs under a GitHub App identity with broad repo scope, has network egress, and — critically — cannot distinguish between the human's task description and adversarial text embedded in the repo content it reads to complete that task. That last property is the whole ballgame.
We've been talking about indirect prompt injection as a theoretical class of attack for two years. GitLost is what it looks like when the theory meets a production agent wired into a source-control system that half the industry ships from. The uncomfortable truth is that every coding agent on the market today — Copilot, Cursor's background agents, Devin, Claude Code in autonomous mode — has the same shape of vulnerability, because they all read untrusted content and act with the user's privileges.
Compare this to the older, saner threat model. A CI job that runs on a pull request from a fork is sandboxed, has scoped secrets, and can't push to the base repo without an approved workflow. Decades of supply-chain incidents taught us that. The Copilot agent gets none of those guardrails by default: it runs with the installing user's access, it reads whatever the task tells it to read, and it can write to any repo the app is installed on. GitHub's own docs frame the agent as an eager junior engineer; GitLost is what happens when that junior engineer takes coding instructions from a stranger who left a Post-it note on their monitor.
The community reaction has been mostly "we told you so," and fairly. Simon Willison has been beating the indirect-prompt-injection drum since 2023. Noma's contribution isn't the class of bug — it's proving that the class of bug survives contact with a specific, widely deployed product. Expect three follow-ons in the next few weeks: (1) other researchers publishing variants against Cursor, Devin, and the Claude Code GitHub App; (2) enterprise security teams demanding kill-switches for agent installs; (3) GitHub shipping some combination of allowlisted domains, per-issue confirmation prompts, and a scarier consent screen.
None of those mitigations are a fix. They're speed bumps. The actual fix — an agent that cryptographically distinguishes trusted instructions from untrusted data — is an unsolved research problem. Until someone solves it, the practical answer is the one the CI world already figured out: don't give the untrusted-input processor the keys to the kingdom.
If you've enabled the Copilot coding agent (or any equivalent) on an org with private repos, three things are worth doing this week.
First, audit the blast radius. In GitHub, the coding agent installs as a GitHub App; check which repos it can see, not just which ones you've assigned it work in. The exfiltration path in GitLost worked because the agent's identity had read access to repos the attacker never named. If your policy is "install on all repos," your policy is "one poisoned issue away from a leak." Narrow it to the specific repos where you actually want agent PRs.
Second, treat the agent's network egress as a secret-handling boundary. The single most effective mitigation available today is restricting where the agent can send data — allowlist GitHub's own APIs, package registries you actually need, and nothing else. If your agent runs in a self-hosted runner or a sandbox you control, put it behind an egress proxy. If it runs on GitHub-hosted infrastructure, lobby your account team for the same knob; several enterprises are already asking.
Third, require human approval on any agent action that touches code outside the assigned repo, references secrets, or hits an unusual URL. Yes, it defeats some of the "autonomous" magic. That's the point. The agent-productivity pitch assumes the agent's actions are correct-by-construction; GitLost is a reminder that they're only correct-by-hope. A code review checkpoint is cheap insurance until the underlying trust model gets better.
For teams still evaluating whether to turn any of this on: the honest calculus right now is that autonomous coding agents are a great fit for public repos and greenfield side projects, and a genuinely risky fit for monorepos that hold customer data, credentials, or unreleased IP. That will change. It hasn't yet.
The interesting question isn't whether GitHub patches GitLost — they will, probably with a domain allowlist and a louder consent screen — but whether the industry finally accepts that "prompt injection is unsolvable at the model layer" means agent architectures have to change. Expect the next 12 months to bring capability-based agent frameworks, signed tool manifests, and a lot more sandboxing between "the LLM read this" and "the LLM can act on this." Until then, the safest place for a coding agent is inside a box small enough that a leak wouldn't matter — and the loudest lesson from GitLost is that most orgs deployed theirs in a box far bigger than they realized.
How is this a Github vulnerability? The researchers are the ones that grant the agent access to private repos and then ask it to answer questions in public repos.. of course this allows extracting private information?This is like setting up a normal CI job with access to secrets and running it on pu
'No Way to Prevent This,' Says Only Programming Concept Where This Regularly Happens
Its funny to see how researchers bypass Githubs praised guardrails with a simple word like "Additionally". It just proves that any attempt to build hard security boundaries inside an llm context window is bound to fail. The model is naturally built to follow instructions, so if you mix sys
> Responsible Disclosure GitLost was responsibly disclosed to GitHub. Vulnerability details are shared here with their knowledge.Why does this section not have when it was fixed or GitHub acknowledge/rejected this?Did they not fix this?
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“Prompt injection attacks have become, to agentic AI, what SQL injections were to web applications: a systematic, category-wide vulnerability class that requires the same systematic strategies and defenses.” ???Isn’t prompt injection far more fatal to LLMs than SQL injection is to SQL databases?Like