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/ruleset/families.toml

@@ -46,6 +46,7 @@ description = "Untrusted data reaches a rendered document or a header without en
 cwes = ["CWE-79", "CWE-80", "CWE-83", "CWE-113", "CWE-116"]
 mechanisms = []
 verifier = "none"
+limits = """Models a value reaching a rendering CALL -- a DOM sink, or a response body written directly. It cannot decide template-mediated escaping, which is the commonest shape a server-rendered application has: whether `res.render` is safe depends on the template engine's autoescape configuration and on the template's own markup, neither of which is at the call. That setting is claimed instead as a configuration defect, where a permissive literal can be read: `swig.setDefaults`, `nunjucks.configure` and Jinja2's `Environment` are security settings in the obligation facts, and turning escaping off is reported by config_secrets. Response splitting (CWE-113) is claimed by no sink here at all, because modern Node rejects a newline in a header value and the claim would be about an engine this project does not model. A scan of a server-rendered application that reports nothing from this family has established that no tainted value reached a modelled rendering call, and nothing about whether its templates escape."""
 
 [[family]]
 id = "untrusted_destination"

src/openultrasast/ruleset/obligations/javascript.toml

@@ -38,6 +38,20 @@ resource_arg = 0
 requires = ["non_permissive_value"]
 sensitivity = "medium"
 
+[[operation]]
+# Template auto-escaping, which is the setting NodeGoat's cross-site scripting actually turns off:
+# `swig.setDefaults({ autoescape: false })` at server.js:135, with `autoescape: true` sitting commented out
+# directly beneath it. The 2026-09-19 family census recorded output encoding completing 44 questions on that
+# repository and finding nothing, because escaping there is a property of the engine's configuration rather
+# than of any call a value flows into. It is a value-shaped defect, so it is claimed here rather than by a
+# flow, and `output_encoding` states this limit in its own declaration.
+id = "template-escaping"
+kind = "security_setting"
+calls = ["swig.setDefaults", "nunjucks.configure", "marked.setOptions"]
+resource_arg = 0
+requires = ["non_permissive_value"]
+sensitivity = "medium"
+
 [[discharger]]
 id = "route-guard"
 kind = "path_guard"
@@ -62,6 +76,16 @@ kind = "non_permissive_value"
 calls = ["cors", "cookie", "session", "helmet", "setHeader"]
 permissive_values = ["'*'", "\"*\"", "true", "0.0.0.0", "null", "false", "origin: true", "secure: false", "httpOnly: false"]
 
+[[discharger]]
+# The polarity of a boolean belongs to the setting, not to the language. `true` leaves the door open in
+# `cors({origin: true})` and closes it in `swig.setDefaults({autoescape: true})`, so these settings carry
+# their OWN permissive value rather than sharing the general one -- which holds both `true` and `false`, and
+# would have reported NodeGoat's commented-out fix as the defect.
+id = "safe-template-escaping"
+kind = "non_permissive_value"
+calls = ["swig.setDefaults", "nunjucks.configure", "marked.setOptions"]
+permissive_values = ["false"]
+
 [[discharger]]
 id = "validated-input"
 kind = "validated_input"

src/openultrasast/ruleset/obligations/python.toml

@@ -68,9 +68,18 @@ id = "safe-setting"
 kind = "non_permissive_value"
 calls = ["CORS", "cross_origin", "set_cookie", "app.run", "config.update", "add_middleware",
          "session_setup", "SimpleCookieStorage", "setup_session", "set_secure_cookie",
-         "Application", "RedisStorage", "Environment"]
+         "Application", "RedisStorage"]
 permissive_values = ["'*'", "\"*\"", "True", "0.0.0.0", "None", "False", "allow_all", "disable"]
 
+[[discharger]]
+# Jinja2's `Environment(autoescape=...)`, moved out of the general list because `True` is in it and `True` is
+# the SAFE value here. Sharing one permissive set made the correct configuration indistinguishable from the
+# dangerous one, which is the same defect the JavaScript template engines would have introduced.
+id = "safe-template-escaping"
+kind = "non_permissive_value"
+calls = ["Environment", "select_autoescape"]
+permissive_values = ["False"]
+
 [[discharger]]
 id = "validated-input"
 kind = "validated_input"

src/openultrasast/ruleset/obligations/typescript.toml

@@ -38,6 +38,20 @@ resource_arg = 0
 requires = ["non_permissive_value"]
 sensitivity = "medium"
 
+[[operation]]
+# Template auto-escaping, which is the setting NodeGoat's cross-site scripting actually turns off:
+# `swig.setDefaults({ autoescape: false })` at server.js:135, with `autoescape: true` sitting commented out
+# directly beneath it. The 2026-09-19 family census recorded output encoding completing 44 questions on that
+# repository and finding nothing, because escaping there is a property of the engine's configuration rather
+# than of any call a value flows into. It is a value-shaped defect, so it is claimed here rather than by a
+# flow, and `output_encoding` states this limit in its own declaration.
+id = "template-escaping"
+kind = "security_setting"
+calls = ["swig.setDefaults", "nunjucks.configure", "marked.setOptions"]
+resource_arg = 0
+requires = ["non_permissive_value"]
+sensitivity = "medium"
+
 [[discharger]]
 id = "route-guard"
 kind = "path_guard"
@@ -62,6 +76,16 @@ kind = "non_permissive_value"
 calls = ["cors", "cookie", "session", "helmet", "setHeader"]
 permissive_values = ["'*'", "\"*\"", "true", "0.0.0.0", "null", "false", "origin: true", "secure: false", "httpOnly: false"]
 
+[[discharger]]
+# The polarity of a boolean belongs to the setting, not to the language. `true` leaves the door open in
+# `cors({origin: true})` and closes it in `swig.setDefaults({autoescape: true})`, so these settings carry
+# their OWN permissive value rather than sharing the general one -- which holds both `true` and `false`, and
+# would have reported NodeGoat's commented-out fix as the defect.
+id = "safe-template-escaping"
+kind = "non_permissive_value"
+calls = ["swig.setDefaults", "nunjucks.configure", "marked.setOptions"]
+permissive_values = ["false"]
+
 [[discharger]]
 id = "validated-input"
 kind = "validated_input"

src/openultrasast/ruleset/semantic/javascript.toml

@@ -57,6 +57,22 @@ cwe = "CWE-79"
 calls = ["innerHTML", "outerHTML", "insertAdjacentHTML", "document.write", "dangerouslySetInnerHTML", "v-html"]
 rule_ids = []
 
+[[sink]]
+# CWE-79, the SERVER half. Every sink above is a DOM sink, so this family could only ever ask about code
+# running in a browser -- and the 2026-09-19 family census recorded it completing 44 questions on a Node
+# application and finding nothing, which is exactly what a client-only vocabulary must do there. These are the
+# documented ways an Express or raw-Node handler puts bytes in a response body without an encoder in between.
+#
+# `res.json` is deliberately absent: it sets an application/json content type, so a value reaching it is not
+# a script in a document. `res.render` is deliberately absent too, and for a different reason -- whether a
+# template escapes is a property of the engine's configuration rather than of the call, so it is claimed as a
+# configuration defect (`swig.setDefaults`, `nunjucks.configure` in the obligation facts) and stated as a
+# limit on this family rather than guessed at here.
+id = "html.response"
+cwe = "CWE-79"
+calls = ["res.write", "res.end", "res.send", "response.write", "response.end", "response.send"]
+rule_ids = []
+
 [[sink]]
 # CWE-22. Node filesystem entry points that accept a caller-supplied path.
 id = "path.open"