Researcher uses Claude Opus and Sonnet to find 100+ flaws in UK government code

A security researcher has found more than 100 serious vulnerabilities in publicly available UK government code, putting sensitive data at risk through poor cyber hygiene, Wired reports. The researcher is Chris Nesbitt-Smith of ControlPlane, and he found the flaws using Claude's Opus and Sonnet AI models.

The UK government has defaulted to openly publishing code it produces with public money for around a decade, because it is transparent and reuse is cost-efficient. That includes the Department of Health and Social Care, the Home Office and local authorities. But funding squeezes have left departments neglecting maintenance and improvement of their technology estate. Nesbitt-Smith says he used consumer-grade models on a laptop, and that many of the issues could have been caught by a routine IT health check. "None of this is the level of sophistication that general media is worried about in terms of cyber attacks," he told Wired. "It's all daft stuff."

The most serious case was at the Planning Inspectorate, which handles land-use matters across England. It had failed to fully remove a login after accidentally committing it to the public repository GitHub. The credentials gave wide access and seemingly did not expire, which, combined with the accidental publication, made the situation particularly dangerous. According to Nesbitt-Smith, the complete Microsoft Entra ID would have given "god-tier" read and write access to all SharePoint sites and private employee OneDrive accounts, including HR records. He says it would also have opened sensitive libraries that safeguard evidence under legal hold for statutory planning inquiries and appeals. "The option for ransomwaring them, for encrypting all the data, or just stealing all the data, was abundantly there," he said.

A Planning Inspectorate spokesperson told Wired that its cyber monitoring tools immediately detected Nesbitt-Smith's activity in August, and that it was already handling the matter as a cyber incident when ControlPlane made contact. The agency identified and fixed the vulnerability within 20 minutes of the report and verified that no data breach occurred. The spokesperson added that it has reviewed and strengthened its systems and processes to prevent a recurrence, and is grateful to the researcher.

Amanda Brock, chief executive officer of nonprofit industry group OpenUK, said the Planning Inspectorate issue "isn't about open source but internal housekeeping when using public tools." She said the data was exposed because of a failure to follow good process, and called it not an open source security issue.

Nesbitt-Smith said he found vulnerabilities in around two-thirds of the 349 public sector codebases across 33 organizations he scanned. Several were in the Department of Education's code: a procurement service used by schools, a teacher application service holding personal details, qualifications, employment history and identity documents, and England's main register of government-funded training providers and apprenticeships. He also found a flaw in a Scottish Government open data portal that would have let any visitor read administrative account information and change site configuration. The organizations have since dealt with the issues.

The findings land amid arguments that public bodies should stop publishing source code in the open, now that AI has accelerated vulnerability discovery. The NHS reportedly ordered technology teams to move away from open source code in May, amid security concerns about the impact of AI models. Nesbitt-Smith says closing code without immediately fixing the underlying problems would be the "worst case scenario": it stops researchers like him from finding the flaws, and an adversary has likely already mirrored the repositories and keeps access. "Unless you're going to go and fix all of the problems, if anything, you're probably drawing more attention to it by closing it," he said.

Key facts

ControlPlane researcher Chris Nesbitt-Smith used Claude's Opus and Sonnet models to find more than 100 serious vulnerabilities in publicly available UK government code.
He says he found vulnerabilities in around two-thirds of the 349 public sector codebases, across 33 organizations, that he scanned.
The worst case was at the Planning Inspectorate: a login accidentally committed to GitHub and not fully removed, which he says would have given broad read and write access across Microsoft services. The agency says it fixed the issue within 20 minutes of the report and that no data breach occurred.
Other flaws touched the Department of Education's code (including a teacher application service) and a Scottish Government open data portal.
Nesbitt-Smith argues that closing code without fixing the underlying problems would be the worst case; OpenUK's Amanda Brock says the Planning Inspectorate case was poor housekeeping, not an open source problem.

Why it matters

The UK government has published its code openly for around a decade, and this is a concrete test of that policy at a time when AI speeds up vulnerability discovery. The story is also a live argument. Some want public bodies to stop publishing code; the NHS reportedly ordered teams to move away from open source in May over AI-related security worries. Nesbitt-Smith's finding is that the flaws were basic, found with consumer-grade models on a laptop, and that hiding code without fixing it would make things worse.

Who it affects

Government bodies that publish code: the Planning Inspectorate, the Department of Education, a Scottish Government open data portal, and the wider set of 33 organizations scanned. Also named as publishers of open code are the Department of Health and Social Care, the Home Office and local authorities. Indirectly it reaches people whose data sits in these systems, such as teachers who applied through the teacher application service, and staff whose HR records sat behind the exposed Planning Inspectorate login.

How to use it

The practical lessons come from the researcher and the case itself. Nesbitt-Smith says many of the issues could have been caught by a routine IT health check. The Planning Inspectorate case came from a login that was committed to a public repository and not fully removed, and the credentials seemingly did not expire. If a team does decide to close its code, he argues, it should fix the underlying problems first, because closing alone only draws attention.

How solid is it

The account comes from Wired and rests largely on Nesbitt-Smith's own statements, including the 'more than 100' count and the scale of access the credentials would have given. The Planning Inspectorate's detection in August, its 20-minute fix and its no-breach verification are the agency's own claims, relayed by Wired. Wired also reports that the affected organizations have since dealt with the issues. The NHS order is reported only as 'reportedly'. The article does not say which Claude versions were used, and does not give a per-organization breakdown of the vulnerabilities.

Risks and caveats

The 'god-tier' access and the ransomware option describe what the credentials would have allowed, not something that happened; the Planning Inspectorate says no data breach occurred. Nesbitt-Smith also says it is likely that an adversary has already mirrored the repositories and keeps access to them. Brock cautions against blaming open source for what she sees as a process failure. The source does not say whether the scanning was authorised by the organizations.

“None of this is the level of sophistication that general media is worried about in terms of cyber attacks”

— Chris Nesbitt-Smith, ControlPlane security researcher, to Wired