Content behind an unopened disclosure

How the text is hidden

The parser records on each open-element frame whether it is a <details> carrying no open attribute. A run is flagged when walking outward from it reaches such a frame, and is not flagged when a <summary> is reached first — the summary is the visible label, and reporting it would be the false half of a true finding.

Why a model still reads it

The content is in the DOM and painted by nothing until the element is opened. Every extractor returns it, so the payload reaches a model and not the human — while the human is shown a summary line and a triangle.

What we do about it

The rule fires on the flag with non-empty text, at informational with action disclose and family B. disclose is the key word: the run's visible state is untouched, so this is a statement that content is there rather than an accusation that the document hid it — the verdict does not move, nothing is stripped, and the finding does not appear in summary.concealedRetained. The argument that a <details> already discloses itself was rejected on direction: a print-only rule makes a payload more visible, and a collapsed fold makes it less.

How often it fires

0.25% of 400 real pages from 400 distinct hosts (Common Crawl) — pages, not documents, measured 2026-08-21.

This is an alert-volume number and nothing else. It says how often the alarm sounds on documents as found — not how often it is right, and not whether what it found was harmless. Documents as found may themselves carry concealment. Read it against the population named above rather than as a property of documents in general.