AIKIDO-2026-276334

TL;DR

The Footnote extension appends the full list of recorded backrefs to every footnote definition block and never removes duplicate definitions of the same label. A document that references one label many times and supplies an equal number of duplicate definitions for it produces a quadratic number of backref nodes. Output size, parse time, and peak memory all grow quadratically, letting a small untrusted input exhaust memory and deny service. The fix keeps only the first definition of each label and stores backrefs under a single key so the amplification no longer occurs.