maskMarkupData terminates an attribute value at the next matching quote anywhere in the document so one unclosed quote erases a raw HTML excluded heading from the scan

maskMarkupData terminates an attribute value at the next matching quote anywhere in the document so one unclosed quote erases a raw HTML excluded heading from the scan

Found by the round-9 adversarial security review of build/itd-183. REGRESSION INTRODUCED BY 2225d6cb -- the parent 044ac6ed refuses this input.

maskMarkupData ends an attribute value at the next matching quote found anywhere in the joined document, not within the tag:

end := strings.IndexByte(s[q+1:], s[q])
if end < 0 { i++; continue }
maskAngles(out, q+1, q+1+end)

So one unclosed attribute quote blanks every < and > up to some unrelated quote thousands of bytes later, erasing a raw-HTML excluded heading from the scan before rawHTMLHeading ever sees it. rawHeadingOpenRe then finds no opener, nothing refuses, no redaction span is recorded, and the heading plus its whole section reaches the bundle under a manifest that asserts the heading was refused.

Minimal reproduction, verified admitted on HEAD and refused on the parent:

---
id: x
---

<div id="

<h2>Audit Notes</h2>

private provenance

">

Same result for <a href='x" >, <img alt="..., <a x='..., and for an opener sitting INSIDE a fenced code block -- the mask is fence-blind, so a fenced <a x=" masks structure outside the fence.

The code comment at project.go:625 asserts the opposite: "none, so an unterminated comment or attribute value makes the scan see MORE". That is untrue. The value is unterminated only relative to its tag; IndexByte pairs it with a quote far away. This is the branch's recurring failure direction -- a mask that answers a false positive by seeing less.

Remedy (class-closing): bound the attribute search to its own tag. Search for the closing quote only within s[q+1:tagEnd], where tagEnd is the first > at or after q IN THE RAW STRING; if no closing quote occurs before it, mask nothing. That makes "unterminated" mean what the comment already claims, and makes the mask incapable of crossing a line the tag never reached.