Text the colour of its background
A run whose text fill is too close to whatever is painted behind it to be read.
How the text is hidden
Two clicks in PowerPoint's ribbon set a shape's fill and then the text's fill to the same colour. The run keeps a normal size and position and sits in the ordinary text stream; on screen there is nothing where the words are. Selecting the area, or changing the fill back, reveals them.
Why a model still reads it
Colour is a style attribute on the run, not a property of the characters. Extraction reads <a:t> and never compares the text fill against the shape fill, so the words arrive intact.
What we do about it
readShapeGround resolves the shape's OWN fill. Where the shape declares no fill, groundBehind supplies what shows through: the topmost earlier-painted shape that fully contains the text box, taking the slide's own shapes over the layout's and master's artwork beneath them. Only when nothing sits behind it does the ground fall back to readSlideBackground's slide -> layout -> master chain.
How often it fires
17.5% 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.
Check your own file
Three commands: a key, credit, a verdict.
Start with the API