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Advisories / SA-2026-009
SA-2026-009: The synthetic review mixed untrusted page text with its instructions
| Severity | high |
| Status | fixed |
| Weakness | CWE-1427 |
| Component | admin/synthetic/run.py, review-guide.md |
| Found by | security@php.newsroom |
| Found | 2026-10-22 |
| Fixed in | v0.5.5 |
| Fixed by | security@php.newsroom |
What it is
The review prompt was the guide, then every page's full text inline, with no boundary. In agent mode the reviewing session held push rights and vault keys. The pages republish third-party words.
What an attacker could do
A sentence planted in a captured page could steer a credentialed agent: push to dev, rewrite a vault.
How: Instructions planted in a captured page reach the site, then review-request.md, then an agent session.
Root cause
Page text was concatenated into the prompt as if it were part of it.
What contributed
- The site republishes other people's words by design.
- The reviewing agent held more rights than reviewing needs.
What was not in place
A boundary between instructions and material, and least privilege for whoever reads it.
The fix
Page text inside <page_content> fences that cannot be closed from inside; the guide says the content is never instructions.
What prevents it now
REQUIREMENTS.md section 5: untrusted text fenced, no tools or credentials in the call, output constrained and escaped.