fix(dep): B7 — token-overlap typosquat heuristic alongside Levenshtein

Critical-review §2 B7 finding: pure Levenshtein <=2 misses the most common
modern typosquat pattern — popular-name + token-injection suffix. Examples:
  lodash → lodash-utils    (edit distance 6, not flagged pre-B7)
  react  → react-helper    (edit distance 7, not flagged pre-B7)
  express → express-wrapper (edit distance 8, not flagged pre-B7)

Three coordinated edits:

scanners/lib/string-utils.mjs
- Adds tokenize(name): string[]    splits on -/_, lowercases
- Adds tokenOverlap(a, b): number  intersection.size / min(|a|,|b|)
- Adds TYPOSQUAT_SUSPICIOUS_TOKENS frozen list of common typosquat
  suffixes. Excludes language-extension tokens (js, jsx, ts, tsx) — the
  v7.0.0 allowlist contains `tsx` as a legit package and including the
  same token in the suspicious set creates a contradiction. Caught by
  the new allowlist-intersection-guard test. Also excludes 'pro'
  (legitimate edition marker).

scanners/dep-auditor.mjs + scanners/supply-chain-recheck.mjs
- New checkTyposquatTokenOverlap() helper — fires AFTER Levenshtein 1/2
  branches, only when:
    1. popular package's tokens ⊆ declared name's tokens (strict superset)
    2. declared name has at least one suspicious suffix
    3. popular package is in topCutoff window
  All three conditions required — conservative by design. Allowlist
  precedence preserved (existing 22 npm + 13 PyPI entries always pass).
  MEDIUM severity, NOT block. New finding title prefix:
  "Possible typosquatting via token-overlap".

Tests: +21 cases across two new files
- tests/lib/string-utils-tokens.test.mjs (15) — tokenize, tokenOverlap,
  TYPOSQUAT_SUSPICIOUS_TOKENS frozen contract, allowlist-intersection
  guard (caught the tsx conflict on first run)
- tests/scanners/dep-token-overlap.test.mjs (7) — integration via
  in-memory tmpdir fixtures: lodash-utils flagged, react-helper flagged,
  express-wrapper flagged, lodash exact NOT flagged, allowlist tools
  (knip/tsx/nx/rimraf) NOT flagged, react-router-dom (no suspicious
  suffix) NOT flagged, react itself (equal token set, not superset)
  NOT flagged.

Existing dep.test.mjs and supply-chain-recheck.test.mjs unchanged —
all green (149 → 149 regression guard).

Suite: 1570 → 1591 (+21). All green.

plugins/llm-security/scanners/dep-auditor.mjs

@@ -6,7 +6,7 @@
 
 import { finding, scannerResult } from './lib/output.mjs';
 import { SEVERITY } from './lib/severity.mjs';
-import { levenshtein } from './lib/string-utils.mjs';
+import { levenshtein, tokenize, tokenOverlap, TYPOSQUAT_SUSPICIOUS_TOKENS } from './lib/string-utils.mjs';
 import { readFile } from 'node:fs/promises';
 import { join, dirname } from 'node:path';
 import { existsSync } from 'node:fs';
@@ -341,6 +341,72 @@ function checkTyposquatting(declaredName, topList, top200Cutoff, ecosystem, sour
     });
   }
 
+  // B7 (v7.2.0): token-overlap heuristic. Flags typosquats that Levenshtein
+  // misses because the attacker added a suspicious suffix token (e.g.
+  // `lodash-utils` vs `lodash`, edit distance 6). Conservative — requires
+  // BOTH a high token-overlap (entire popular name's tokens are a subset
+  // of the declared name) AND at least one suspicious suffix token.
+  const tokenOverlapFinding = checkTyposquatTokenOverlap(
+    declaredName,
+    topList,
+    top200Cutoff,
+    ecosystem,
+    sourceFile,
+  );
+  if (tokenOverlapFinding) return tokenOverlapFinding;
+
+  return null;
+}
+
+/**
+ * B7 token-overlap heuristic — complementary to Levenshtein. Returns a
+ * MEDIUM finding when:
+ *   1. The declared name's tokens contain ALL of a popular package's tokens
+ *      (popular package's tokens ⊆ declared name's tokens), AND
+ *   2. The declared name has at least one suspicious suffix token
+ *      (`-utils`, `-helper`, `-pro`, `-cli`, `-wrapper`, etc.), AND
+ *   3. The popular package is in the top200Cutoff window
+ *
+ * Returns null if no match. Allowlist precedence is enforced by the caller
+ * (returning null at the top of `checkTyposquatting` before this is reached).
+ */
+function checkTyposquatTokenOverlap(declaredName, topList, top200Cutoff, ecosystem, sourceFile) {
+  const declaredTokens = new Set(tokenize(declaredName));
+  if (declaredTokens.size < 2) return null;
+
+  const suspiciousSuffixes = TYPOSQUAT_SUSPICIOUS_TOKENS.filter(t => declaredTokens.has(t));
+  if (suspiciousSuffixes.length === 0) return null;
+
+  const limit = Math.min(top200Cutoff, topList.length);
+  for (let i = 0; i < limit; i++) {
+    const topPkg = topList[i];
+    if (declaredName === topPkg) return null;
+    const topTokens = tokenize(topPkg);
+    if (topTokens.length === 0) continue;
+    const allContained = topTokens.every(t => declaredTokens.has(t));
+    if (!allContained) continue;
+    if (topTokens.length === declaredTokens.size) continue; // exact-token-set is not a typosquat
+    const overlap = tokenOverlap(declaredName, topPkg);
+    if (overlap < 0.66) continue;
+    return finding({
+      scanner: 'DEP',
+      severity: SEVERITY.MEDIUM,
+      title: `Possible typosquatting via token-overlap: "${declaredName}" vs "${topPkg}"`,
+      description:
+        `The declared ${ecosystem} package "${declaredName}" contains all tokens of the ` +
+        `popular package "${topPkg}" plus a suspicious suffix (${suspiciousSuffixes.join(', ')}). ` +
+        `This is a common typosquat pattern: attackers register popular-name-plus-suffix ` +
+        `packages to capture installs from users misremembering the canonical name.`,
+      file: sourceFile,
+      evidence: `"${declaredName}" tokens ⊃ "${topPkg}" tokens; suffix=${suspiciousSuffixes.join(',')}; overlap=${overlap.toFixed(2)}`,
+      owasp: 'LLM03',
+      recommendation:
+        `Verify that "${declaredName}" is intentional. If you meant "${topPkg}", ` +
+        `correct the dependency name. If "${declaredName}" is a legitimate utility ` +
+        `package, add it to knowledge/typosquat-allowlist.json under "${ecosystem}".`,
+    });
+  }
+
   return null;
 }
 

plugins/llm-security/scanners/lib/string-utils.mjs

@@ -54,6 +54,72 @@ export function levenshtein(a, b) {
   return prev[n];
 }
 
+/**
+ * Split a package name into lowercase tokens on `-` and `_` boundaries.
+ * Used by the B7 typosquat token-overlap heuristic. Empty tokens are
+ * dropped. Single-character tokens are kept (some package names like
+ * `a-b` are real).
+ *
+ * @param {string} name
+ * @returns {string[]}
+ */
+export function tokenize(name) {
+  if (!name) return [];
+  return name
+    .toLowerCase()
+    .split(/[-_]+/)
+    .filter(t => t.length > 0);
+}
+
+/**
+ * Token-overlap ratio between two package names. Returns the size of the
+ * intersection divided by the size of the smaller token set. Returns 0 if
+ * either input is empty.
+ *
+ * Example: `tokenOverlap('lodash-utils', 'lodash')` → 1.0
+ *          `tokenOverlap('react-router-dom', 'react')` → 1.0
+ *          `tokenOverlap('react-helper', 'react-router')` → 0.5
+ *          `tokenOverlap('foo', 'bar')` → 0.0
+ *
+ * Used by B7 (v7.2.0) as a complementary signal alongside Levenshtein —
+ * Levenshtein <=2 catches small typos; token-overlap catches
+ * popular-name-with-suffix typosquats.
+ *
+ * @param {string} a
+ * @param {string} b
+ * @returns {number}  0..1
+ */
+export function tokenOverlap(a, b) {
+  const ta = new Set(tokenize(a));
+  const tb = new Set(tokenize(b));
+  if (ta.size === 0 || tb.size === 0) return 0;
+  let intersection = 0;
+  for (const t of ta) if (tb.has(t)) intersection++;
+  return intersection / Math.min(ta.size, tb.size);
+}
+
+/**
+ * Suspicious suffix tokens commonly used by typosquats to dress up a
+ * popular package name. Module-level for B7 reuse.
+ *
+ * Excluded by design (would conflict with the v7.0.0 typosquat allowlist
+ * or trigger false positives on legitimate packages):
+ *   - `js`, `jsx`, `ts`, `tsx` — language-extension suffixes used by many
+ *     legitimate packages (`react-jsx`, the `tsx` runtime, etc.). The
+ *     v7.0.0 allowlist contains `tsx` directly; including the same token
+ *     in the suspicious set would create an internal contradiction.
+ *   - `pro` — too common as a legitimate edition marker (`vue-pro`,
+ *     `tailwindcss-pro`).
+ *
+ * Kept tokens are the unambiguous typosquat suffixes: utility/helper
+ * dressing, wrapper/shim packages, and tool/cli/sdk/kit qualifiers.
+ */
+export const TYPOSQUAT_SUSPICIOUS_TOKENS = Object.freeze([
+  'utils', 'util', 'helper', 'helpers', 'core', 'plus', 'extra', 'extras',
+  'bin', 'cli', 'tool', 'tools',
+  'wrapper', 'wrappers', 'lib', 'libs', 'kit', 'sdk', 'shim',
+]);
+
 /**
  * Check if a string looks like base64-encoded data.
  * @param {string} s

plugins/llm-security/scanners/supply-chain-recheck.mjs

@@ -16,7 +16,7 @@ import { existsSync, readFileSync } from 'node:fs';
 import { fileURLToPath } from 'node:url';
 import { finding, scannerResult } from './lib/output.mjs';
 import { SEVERITY } from './lib/severity.mjs';
-import { levenshtein } from './lib/string-utils.mjs';
+import { levenshtein, tokenize, tokenOverlap, TYPOSQUAT_SUSPICIOUS_TOKENS } from './lib/string-utils.mjs';
 import {
   NPM_COMPROMISED, PIP_COMPROMISED, CARGO_COMPROMISED, GEM_COMPROMISED,
   isCompromised, extractOSVSeverity, queryOSVBatch, OSV_ECOSYSTEM_MAP,
@@ -337,11 +337,55 @@ function checkTyposquatting(deps, topList, topCutoff, ecosystem, lockfile, allow
         recommendation:
           `Confirm "${dep.name}" is the correct package. Check publish date and author on the registry.`,
       }));
+    } else {
+      // B7 (v7.2.0): token-overlap fallback. Catches typosquats with edit
+      // distance >= 3 that contain all tokens of a popular package plus a
+      // suspicious suffix (e.g. `lodash-utils` vs `lodash`).
+      const tokenFinding = checkTyposquatTokenOverlap(dep, normalized, topList, topCutoff, ecosystem, lockfile);
+      if (tokenFinding) results.push(tokenFinding);
     }
   }
   return results;
 }
 
+function checkTyposquatTokenOverlap(dep, normalized, topList, topCutoff, ecosystem, lockfile) {
+  const declaredTokens = new Set(tokenize(normalized));
+  if (declaredTokens.size < 2) return null;
+
+  const suspiciousSuffixes = TYPOSQUAT_SUSPICIOUS_TOKENS.filter(t => declaredTokens.has(t));
+  if (suspiciousSuffixes.length === 0) return null;
+
+  const limit = Math.min(topCutoff, topList.length);
+  for (let i = 0; i < limit; i++) {
+    const topPkg = topList[i];
+    if (normalized === topPkg) return null;
+    const topTokens = tokenize(topPkg);
+    if (topTokens.length === 0) continue;
+    const allContained = topTokens.every(t => declaredTokens.has(t));
+    if (!allContained) continue;
+    if (topTokens.length === declaredTokens.size) continue;
+    const overlap = tokenOverlap(normalized, topPkg);
+    if (overlap < 0.66) continue;
+    return finding({
+      scanner: 'SCR',
+      severity: SEVERITY.MEDIUM,
+      title: `Possible typosquatting via token-overlap: "${dep.name}" vs "${topPkg}"`,
+      description:
+        `"${dep.name}" in ${lockfile} contains all tokens of the popular ${ecosystem} package ` +
+        `"${topPkg}" plus a suspicious suffix (${suspiciousSuffixes.join(', ')}). ` +
+        `This is a common typosquat pattern: attackers register popular-name-plus-suffix ` +
+        `packages to capture installs.`,
+      file: lockfile,
+      evidence: `"${dep.name}" tokens ⊃ "${topPkg}" tokens; suffix=${suspiciousSuffixes.join(',')}; overlap=${overlap.toFixed(2)}`,
+      owasp: 'LLM03',
+      recommendation:
+        `Verify "${dep.name}" is intentional. If you meant "${topPkg}", correct the dependency. ` +
+        `If "${dep.name}" is a legitimate utility, add it to knowledge/typosquat-allowlist.json under "${ecosystem}".`,
+    });
+  }
+  return null;
+}
+
 // ---------------------------------------------------------------------------
 // Main scanner export
 // ---------------------------------------------------------------------------