Alt text on slide shapes

How the text is hidden

A shape's non-visual properties element p:cNvPr carries descr and title attributes — the Alt Text pane in PowerPoint. The value is arbitrary text of arbitrary length attached to an object on the slide. It is never drawn: it exists so assistive technology can describe the object.

Why a model still reads it

Alt text is exactly the field a document extractor is expected to surface, since a picture has no other textual content. It comes through as prose with no marker separating a description from the slide's own words.

What we do about it

Severity is informational and the finding is flagged: alt text is authored accessibility content rather than concealment, so grading every description as a warning would make ordinary accessibility work look suspicious. R-5a escalates it to high the moment the description is instruction-shaped, and the finding withdraws certified at any severity.

How often it fires

10% of 120 real Zenodo conference decks (corpus-zenodopptx as re-fetched 2026-08-23), measured 2026-08-24.

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.