Critical-review §4 E16 finding: pre-v7.2.0 homoglyph normalization fired
ONLY for the MEDIUM-advisory "obfuscation present" signal. Pattern
matchers in scanForInjection compared against raw + decoded variants
only — they did NOT compare against a fold-normalized variant. As a
result, "ignоre previous instructions" (Cyrillic о, U+043E) bypassed
the CRITICAL "ignore previous" pattern.
Two coordinated edits:
scanners/lib/string-utils.mjs
- Adds HOMOGLYPH_MAP (frozen) — surgical Cyrillic/Greek → Latin map.
~25 entries focused on injection-vocabulary letters
(a, e, o, c, p, x, y, i, j, s, l, A, E, O, C, P, X, Y, T).
- Adds foldHomoglyphs(s) — pipeline: NFKC → apply HOMOGLYPH_MAP.
NFKC handles Mathematical Alphanumeric (U+1D400 block), fullwidth
Latin (U+FF21 block), ligatures, width variants.
Excluded by design from HOMOGLYPH_MAP:
- Latin Extended (æ, ø, å, é, è, ñ, ü, ö, ä, ç, ß, þ, ð) — legitimate
Norwegian/German/French/Spanish letters. Map them and we false-positive
on every non-English source file.
- Greek letters not visually overlapping (β, γ, δ, ...)
- Cyrillic letters not visually overlapping (б, г, д, ж, ...)
scanners/lib/injection-patterns.mjs
- scanForInjection now builds a 4-variant set: raw, normalized,
folded(raw), folded(normalized). Set deduplication skips redundant
identical variants. Existing dedup-by-label (seenLabels Set) prevents
double-counts when the same pattern matches in multiple variants.
- foldHomoglyphs added to the imports.
Tests: +27 cases in tests/lib/string-utils-homoglyph.test.mjs:
- 6 Cyrillic → Latin (lowercase, uppercase, multiple substitutions,
Palochka U+04CF)
- 3 Greek → Latin
- 2 NFKC normalization (Math Bold, Fullwidth)
- 8 preserves-non-confusable (Norwegian æøå, German umlauts, French
accents, Spanish ñ, emoji, CJK, Arabic/Hebrew)
- 3 edge cases (empty, null/undefined, idempotency)
- 5 scanForInjection integration (Cyrillic ignore, Cyrillic Assistant,
Norwegian non-trigger, benign "ignore" comment, mixed Cyrillic+Greek)
Test-development found: U+1D5DC is "I" not "A" (test pin caught my
codepoint mistake — fixed during dev).
Suite: 1617 → 1644 (+27). All green.
