fix(output-encoding): ask about the server half, and say what the family cannot decide

The census recorded this family completing 44 questions on a Node application and finding
nothing, which is what a client-only vocabulary must do there: all six declared sinks were DOM
sinks. NodeGoat's cross-site scripting is server-side.

Decision: the family asks about a value reaching a rendering call, and states in its own
declaration that it cannot decide template-mediated escaping. Whether res.render is safe depends
on the engine's autoescape setting and on the template's markup, neither of which is at the
call, so res.render is not a sink and the family's limits field says so. A new CWE-79 sink
covers res.write, res.end, res.send and the response.* spellings; res.json stays out because an
application/json body is not a document.

Template auto-escaping is claimed where its evidence is, as a configuration defect:
swig.setDefaults, nunjucks.configure and marked.setOptions are security settings now.

It establishes a finding: app/routes/research.js:25, model_entailed,
`req.query.url + req.query.symbol -> res.write(body)`. The handler fetches a URL the caller
chooses and writes the response body into a text/html response, so the document served from
this origin is the attacker's. The record states how coarse the step is: the path from url to
body runs through the client's callback parameter, which the graph treats as reachable from the
call's arguments, so the conclusion rests on the call's semantics rather than on what the graph
established. Five of seven families now establish findings.

Four defects were found on the way, three of them false positives this change would otherwise
have shipped.

- The permissive-value set was shared across every setting, while a boolean's polarity belongs
  to the setting: true leaves the door open in cors({origin: true}) and closes it in
  swig.setDefaults({autoescape: true}). Adding the template engines would have reported the fix
  as the defect on the line that offers it. ConfigSpec now carries per-setting values, and
  Jinja2's Environment moved out of Python's shared list for the same latent reason.
- config.sc matched a dotted setting on its trailing segment alone, so marked.setOptions would
  have claimed an editor's setOptions. dominance.sc already required the qualifier.
- taint.sc asked its flow query of every argument including the receiver at index 0. On a
  response sink the receiver is the response object, so res.end() -- which takes no data -- was
  reported exactly like the res.write(body) two lines above it. Flows now use the real
  arguments, as arity already did.
- The arbiter sorted a file's settings by line number as TEXT, so line 126 preceded line 78 and
  which setting a file reported depended on the spelling of its line numbers.

Template escaping disabled at server.js:135 is detected, measured model_entailed against the
real query and the real arbiter, and still not reported: the arbiter returns one verdict per
question and that file has an earlier permissive setting. Task 14.6 carries it rather than
hiding it.

1,415 tests pass, thirteen skipped; nine Joern-gated query tests pass in the image.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

src/openultrasast/cpg/queries/config.sc

@@ -38,10 +38,22 @@
   val names = split(settingsS)
   val function = functionS
 
-  def matches(name: String): Boolean = names.exists(n => name == n || name == n.split("\\.").last)
+  // A dotted spec matches on its trailing segment, which is how the call is named in the graph -- but the
+  // qualification has to matter, or the segment alone claims every unrelated call that ends the same way.
+  // `marked.setOptions` would otherwise match an editor's `setOptions` and `nunjucks.configure` any
+  // `configure` at all. dominance.sc carries this fix and the reason for it; the setting matcher had never
+  // been given the same treatment, and it became load-bearing when the template engines joined the table.
+  def matches(name: String, code: String): Boolean =
+    names.exists { n =>
+      if (name == n) true
+      else {
+        val parts = n.split("\\.")
+        parts.length > 1 && name == parts.last && parts.init.forall(q => code.contains(q))
+      }
+    }
 
   val calls = {
-    val all = cpg.call.filter(c => matches(c.name)).l
+    val all = cpg.call.filter(c => matches(c.name, c.code)).l
     val inFile = if (fileS.isEmpty) all else all.filter(_.method.filename.endsWith(fileS))
     if (function.isEmpty) inFile else inFile.filter(_.method.name == function)
   }

src/openultrasast/cpg/queries/taint.sc

@@ -772,7 +772,12 @@
     // makes a one-argument interpolated call look like a two-argument bound one -- the exact inversion of the
     // test. Real arguments start at index 1.
     val realArgs = sink.argument.argumentIndexGt(0).l
-    val flows    = if (hasSources) sink.argument.reachableByFlows(sourceNodes).l else Nil
+    // Asked of the REAL arguments, for the same reason arity is counted over them. `call.argument` carries the
+    // receiver at index 0, and on a response sink the receiver is the response object itself: `res.end()` takes
+    // no data at all, yet `res` is reachable from the request in any handler that captures it, so the flow
+    // query answered yes about a call that receives nothing. Measured on NodeGoat, where `res.write(body)` is a
+    // real finding and `res.end()` two lines below it was reported identically.
+    val flows = if (hasSources) sink.argument.argumentIndexGt(0).reachableByFlows(sourceNodes).l else Nil
 
     // The SHAPE of the sink call, which is what distinguishes a fix from a bug when the fix is a safe form
     // rather than a sanitizing call: `execute(sql, params)` binds where `execute(sql + x)` interpolates, and