Harden serve defaults and close XSS/path injection sinks.

Make tracer serve loopback-only with opt-in CORS and request/batch caps, escape untrusted report/scan content (including sankey/viz), and allowlist watch sink filenames so local telemetry cannot traverse the filesystem.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: batmnnn

.gitignore

@@ -35,3 +35,15 @@ notebooks/data/
 
 # Node (JS package)
 node_modules/
+
+# Secrets / credentials (never commit)
+.env
+.env.*
+!.env.example
+*.pem
+*.key
+credentials.json
+cloud.json
+
+# Local agent/security tooling
+.superstack/

AGENTS.md

@@ -155,8 +155,9 @@ router = tracer.load_router(".tracer", embedder=my_embedder)
 
 ### Pattern 4: HTTP server (zero deps)
 ```bash
-tracer serve .tracer --port 8000
+tracer serve .tracer --port 8000          # binds 127.0.0.1 by default (no auth)
 # POST /predict {"embedding": [...]} → {"label", "decision", "accept_score"}
+# Only use --host 0.0.0.0 behind a reverse proxy with TLS/auth. .tracer artifacts are trusted code (joblib/pickle).
 ```
 
 ---

SECURITY.md

@@ -45,4 +45,18 @@ own API keys; issues in third-party dependencies, model providers, or your own
 deployment configuration are out of scope here — please report those to the
 relevant vendor.
 
+## Trust model (operators)
+
+A few boundaries that matter when deploying Tracer:
+
+- **`.tracer` artifacts are trusted code.** `pipeline.joblib` is loaded with
+  joblib/pickle. Only load artifacts you produced (or otherwise fully trust).
+  Treat a foreign `.tracer/` directory like an untrusted binary.
+- **`tracer serve` has no authentication.** It binds to `127.0.0.1` by default.
+  If you bind to `0.0.0.0` (or otherwise expose the port), put a reverse proxy
+  with TLS and auth in front. CORS is off unless you pass `--cors-origin`.
+- **`tracer.watch` / `@tracer-llm/watch` may exfiltrate prompts.** When
+  `TRACER_CLOUD_KEY` (or an OTLP endpoint) is set, full input/output text is
+  sent to that destination. Keep those env vars under your control.
+
 Thank you for helping keep Tracer and its users safe.

docs/cli.md

@@ -339,7 +339,10 @@ tracer serve [<artifact-dir>] [--host <addr>] [--port <int>]
 | Argument | Default | Description |
 |----------|---------|-------------|
 | `artifact-dir` | `.tracer` | Artifact directory |
-| `--host` | `0.0.0.0` | Bind address |
+| `--host` | `127.0.0.1` | Bind address (loopback; use `0.0.0.0` only behind a reverse proxy with auth) |
+| `--cors-origin` | off | If set, emit `Access-Control-Allow-Origin` (e.g. `https://app.example.com` or `*`) |
+| `--max-body-bytes` | `16777216` | Reject larger request bodies |
+| `--max-batch` | `10000` | Reject `/predict_batch` with more rows |
 | `--port` | `8000` | Listen port |
 
 **Endpoints:**

docs/javascript.md

@@ -81,7 +81,7 @@ TRACER reads `traces.jsonl` and auto-discovers `traces.npy` (same stem, `.npy` e
 tracer serve .tracer --port 8000
 ```
 
-Run this as a sidecar next to your Node app, same server, same docker-compose, same machine. It binds to `0.0.0.0:8000` by default.
+Run this as a sidecar next to your Node app, same server, same docker-compose, same machine. It binds to `127.0.0.1:8000` by default (pass `--host 0.0.0.0` only behind a reverse proxy with auth).
 
 ---
 

js/src/index.ts

@@ -372,16 +372,35 @@ function getEnv(name: string): string | undefined {
   return g.process?.env?.[name];
 }
 
+const WATCH_NAME_RE = /^[A-Za-z0-9][A-Za-z0-9._-]{0,127}$/;
+
+/** Allowlist watcher names used as filenames (no path separators / traversal). */
+export function safeWatchName(name: string): string {
+  if (typeof name !== "string" || !WATCH_NAME_RE.test(name)) {
+    throw new Error(
+      `invalid watch name ${JSON.stringify(name)}: use 1-128 chars of [A-Za-z0-9._-], starting with alphanumeric`,
+    );
+  }
+  return name;
+}
+
 /** Append spans as JSONL to `<dir>/<name>.jsonl`. No network, no key. */
 export class LocalFileSink implements Sink {
   readonly path: string;
   constructor(name: string, dir: string = ".tracer/watch") {
-    this.path = path.join(dir, `${name}.jsonl`);
+    const safe = safeWatchName(name);
+    const root = path.resolve(dir);
     try {
-      fs.mkdirSync(dir, { recursive: true });
+      fs.mkdirSync(root, { recursive: true });
     } catch (e) {
-      debugLog(`could not create dir ${dir}: ${String(e)}`);
+      debugLog(`could not create dir ${root}: ${String(e)}`);
+    }
+    const full = path.resolve(root, `${safe}.jsonl`);
+    const rel = path.relative(root, full);
+    if (rel.startsWith("..") || path.isAbsolute(rel)) {
+      throw new Error(`watch path escapes directory: ${JSON.stringify(name)}`);
     }
+    this.path = full;
   }
 
   emit(span: GenAISpan): void {

js/test/watch.test.ts

@@ -71,6 +71,13 @@ describe("GenAISpan", () => {
 
 // ----- LocalFileSink --------------------------------------------------------- //
 describe("LocalFileSink", () => {
+  it("rejects unsafe watch names (allowlist)", () => {
+    const dir = tmpDir();
+    for (const bad of ["../evil", "..\\evil", "a/b", "..", "", "has space", "-leading"]) {
+      expect(() => new LocalFileSink(bad, dir)).toThrow(/invalid watch name/);
+    }
+  });
+
   it("writes JSONL", () => {
     const dir = tmpDir();
     const sink = new LocalFileSink("unit", dir);

src/tracer/analysis/html_report.py

@@ -3,9 +3,18 @@
 from __future__ import annotations
 
 import json
+from html import escape as _html_escape
 from pathlib import Path
 from typing import Union
 
+# Pin Plotly (no "latest"); only injected when a sankey div is rendered.
+_PLOTLY_CDN = "https://cdn.plot.ly/plotly-2.35.2.min.js"
+
+
+def _esc(value) -> str:
+    """HTML-escape dynamic report fields (XSS-safe)."""
+    return _html_escape("" if value is None else str(value), quote=True)
+
 
 _CSS = """
 * { box-sizing: border-box; margin: 0; padding: 0; }
@@ -222,11 +231,26 @@ def generate_html_report(
     method      = manifest_raw.get("selected_method") or "none"
     coverage    = manifest_raw.get("coverage_cal")
     ta          = manifest_raw.get("teacher_agreement_cal")
-    n_traces    = manifest_raw.get("n_traces", 0)
-    n_labels    = len(manifest_raw.get("label_space", []))
-    emb_dim     = manifest_raw.get("embedding_dim")
-    target_ta   = manifest_raw.get("target_teacher_agreement", 0.90)
-    method_cls  = _METHOD_BADGE.get(method, "b-gray")
+    # Coerce numerics — manifest fields are untrusted if the artifact is.
+    try:
+        n_traces = int(manifest_raw.get("n_traces", 0) or 0)
+    except (TypeError, ValueError):
+        n_traces = 0
+    label_space = manifest_raw.get("label_space") or []
+    n_labels = len(label_space) if isinstance(label_space, list) else 0
+    try:
+        emb_dim = int(manifest_raw["embedding_dim"]) if manifest_raw.get("embedding_dim") is not None else None
+    except (TypeError, ValueError):
+        emb_dim = None
+    try:
+        target_ta = float(manifest_raw.get("target_teacher_agreement", 0.90) or 0.90)
+    except (TypeError, ValueError):
+        target_ta = 0.90
+    # Only allow known badge classes (manifest method is untrusted input).
+    method_cls  = _METHOD_BADGE.get(method) or "b-gray"
+    if method_cls not in ("b-green", "b-blue", "b-purple", "b-gray"):
+        method_cls = "b-gray"
+    emb_dim_disp = str(emb_dim) if emb_dim is not None else "?"
 
     cov_exact = (coverage or 0) * 100
     defer_exact = 100 - cov_exact
@@ -261,10 +285,7 @@ def generate_html_report(
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>Tracer routing report</title>
-<link rel="preconnect" href="https://fonts.googleapis.com">
-<link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;700&family=Manrope:wght@500;700;800&display=swap" rel="stylesheet">
 <style>{_CSS}</style>
-<script src="https://cdn.plot.ly/plotly-latest.min.js"></script>
 </head>
 <body>
 <div class="page">
@@ -278,7 +299,7 @@ def generate_html_report(
 <h1>Routing Policy</h1>
 <div class="subtitle">
   {n_traces:,} traces &nbsp;·&nbsp; {n_labels} labels
-  &nbsp;·&nbsp; {emb_dim}-dim embeddings
+  &nbsp;·&nbsp; {_esc(emb_dim_disp)}-dim embeddings
   &nbsp;·&nbsp; target TA = {target_ta:.0%}
 </div>
 
@@ -296,7 +317,7 @@ def generate_html_report(
   <div class="card purple">
     <div class="card-label">Method</div>
     <div class="card-value" style="font-size:1.2rem;margin-top:10px">
-      <span class="badge {method_cls}">{method.upper()}</span>
+      <span class="badge {method_cls}">{_esc(method.upper())}</span>
     </div>
     <div class="card-sub">selected pipeline</div>
   </div>
@@ -355,6 +376,7 @@ def generate_html_report(
             from tracer.analysis.sankey import generate_sankey_div
             sankey_div = generate_sankey_div(artifact_dir)
             if sankey_div:
+                html += f'<script src="{_PLOTLY_CDN}"></script>\n'
                 html += f"""
 <div class="section">
   <h2>Routing Flow</h2>
@@ -389,16 +411,16 @@ def generate_html_report(
     <tbody>
 """
         for s in sorted(label_slices, key=lambda x: -x["handled_rate"]):
-            label = s["slice_name"].replace("label:", "")
+            label = _esc(s["slice_name"].replace("label:", ""))
             hr_v  = s["handled_rate"]
             ta_s  = s.get("teacher_agreement_handled")
             ta_str = f"{ta_s:.1%}" if ta_s is not None else "-"
             html += (
                 f'<tr><td><code style="color:#8b949e;font-size:.82rem">{label}</code></td>'
                 f'<td><b style="color:#f0f6fc">{hr_v:.1%}</b></td>'
                 f'<td>{_bar_html(hr_v)}</td>'
-                f'<td style="color:#8b949e">{s["count"]}</td>'
-                f'<td style="color:#8b949e">{ta_str}</td></tr>\n'
+                f'<td style="color:#8b949e">{int(s["count"])}</td>'
+                f'<td style="color:#8b949e">{_esc(ta_str)}</td></tr>\n'
             )
         html += "    </tbody>\n  </table>\n</div>\n"
 
@@ -408,10 +430,10 @@ def generate_html_report(
             html += '<tr><th>Bucket</th><th>Coverage</th><th style="width:130px"></th><th>Count</th></tr>\n'
             for s in length_slices:
                 html += (
-                    f'<tr><td>{s["slice_name"]}</td>'
+                    f'<tr><td>{_esc(s["slice_name"])}</td>'
                     f'<td><b style="color:#f0f6fc">{s["handled_rate"]:.1%}</b></td>'
                     f'<td>{_bar_html(s["handled_rate"])}</td>'
-                    f'<td style="color:#8b949e">{s["count"]}</td></tr>\n'
+                    f'<td style="color:#8b949e">{int(s["count"])}</td></tr>\n'
                 )
             html += '</table>\n</div>\n'
 
@@ -423,14 +445,14 @@ def generate_html_report(
                 hs = _score_str(p.get("handled_score"))
                 ds = _score_str(p.get("deferred_score"))
                 html += f"""<div class="pair">
-  <div class="pair-intent">{p["teacher_label"]}</div>
+  <div class="pair-intent">{_esc(p["teacher_label"])}</div>
   <div class="pair-row">
     <span class="pair-tag pt-local">SURROGATE</span>
-    <span class="pair-text">{p["handled_preview"]}</span>{hs}
+    <span class="pair-text">{_esc(p["handled_preview"])}</span>{hs}
   </div>
   <div class="pair-row">
     <span class="pair-tag pt-deferred">→ LLM</span>
-    <span class="pair-text">{p["deferred_preview"]}</span>{ds}
+    <span class="pair-text">{_esc(p["deferred_preview"])}</span>{ds}
   </div>
 </div>\n"""
             html += '</div>\n'
@@ -443,18 +465,18 @@ def generate_html_report(
             for ex in handled_ex[:6]:
                 score_str = f'<span class="ex-score">score {ex["accept_score"]:.2f}</span>' if ex.get("accept_score") else ""
                 html += (f'<div class="ex-item handled">'
-                         f'<div class="ex-text">{ex["input_preview"]}</div>'
+                         f'<div class="ex-text">{_esc(ex["input_preview"])}</div>'
                          f'<div class="ex-meta">'
-                         f'<span class="ex-label">{ex["teacher_label"]}</span>'
+                         f'<span class="ex-label">{_esc(ex["teacher_label"])}</span>'
                          f'{score_str}</div></div>\n')
             html += '</div>\n'
 
             html += '<div class="ex-col">\n<h3>Deferred to teacher</h3>\n'
             for ex in deferred_ex[:6]:
                 html += (f'<div class="ex-item deferred">'
-                         f'<div class="ex-text">{ex["input_preview"]}</div>'
+                         f'<div class="ex-text">{_esc(ex["input_preview"])}</div>'
                          f'<div class="ex-meta">'
-                         f'<span class="ex-label">{ex["teacher_label"]}</span>'
+                         f'<span class="ex-label">{_esc(ex["teacher_label"])}</span>'
                          f'</div></div>\n')
             html += '</div>\n'
 
@@ -470,7 +492,7 @@ def generate_html_report(
                 prev_bar = int(d["previous_handled_rate"] * 60)
                 cur_bar  = int(d["current_handled_rate"] * 60)
                 html += (
-                    f'<tr><td><code style="color:#8b949e;font-size:.82rem">{d["label"]}</code></td>'
+                    f'<tr><td><code style="color:#8b949e;font-size:.82rem">{_esc(d["label"])}</code></td>'
                     f'<td style="color:#8b949e">{d["previous_handled_rate"]:.1%}'
                     f'<div class="delta-bar-bg"><div class="delta-bar-fill" style="width:{prev_bar}px"></div></div></td>'
                     f'<td style="color:#f0f6fc">{d["current_handled_rate"]:.1%}'

src/tracer/analysis/sankey.py

@@ -3,9 +3,20 @@
 from __future__ import annotations
 
 import json
+import re
 from pathlib import Path
 from typing import Optional, Union
 
+# Labels are embedded into Plotly HTML/JS. Strip markup metacharacters so a
+# poisoned teacher label cannot break out of the inline <script> payload.
+_UNSAFE_LABEL = re.compile(r"""[<>&"'`\\]""")
+
+
+def _safe_node_label(text: str, *, max_len: int = 120) -> str:
+    cleaned = _UNSAFE_LABEL.sub("", str(text))
+    cleaned = "".join(ch for ch in cleaned if ch.isprintable() or ch in " \t")
+    return cleaned[:max_len] if cleaned else "(label)"
+
 
 _PALETTE = [
     "#4f7cac", "#7fb069", "#e0a458", "#c97b84", "#8f7aa7",
@@ -131,15 +142,18 @@ def _build_sankey_figure(manifest: dict, qr: dict, top_k: int, dark: bool):
     n_other_labels = len(manifest.get("label_space", [])) - n_top
     has_other = (other_handled + other_deferred) > 0.5
 
-    node_labels = [s["slice_name"].replace("label:", "").replace("_", " ") for s in top]
+    node_labels = [
+        _safe_node_label(s["slice_name"].replace("label:", "").replace("_", " "))
+        for s in top
+    ]
     if has_other:
-        node_labels.append(f"other ({n_other_labels} labels)")
+        node_labels.append(_safe_node_label(f"other ({n_other_labels} labels)"))
     surrogate_idx = len(node_labels)
     teacher_idx = surrogate_idx + 1
     pct_h = coverage * 100
     pct_d = (1 - coverage) * 100
-    node_labels.append(f"Surrogate  ({pct_h:.0f}%)")
-    node_labels.append(f"Teacher / LLM  ({pct_d:.0f}%)")
+    node_labels.append(_safe_node_label(f"Surrogate  ({pct_h:.0f}%)"))
+    node_labels.append(_safe_node_label(f"Teacher / LLM  ({pct_d:.0f}%)"))
 
     if dark:
         _palette_dark = [

src/tracer/cli/main.py

@@ -174,7 +174,14 @@ def _cmd_sankey(args):
 
 def _cmd_serve(args):
     from tracer.runtime.serve import serve
-    serve(artifact_dir=args.artifact_dir, host=args.host, port=args.port)
+    serve(
+        artifact_dir=args.artifact_dir,
+        host=args.host,
+        port=args.port,
+        cors_origin=args.cors_origin,
+        max_body_bytes=args.max_body_bytes,
+        max_batch=args.max_batch,
+    )
 
 
 def _cmd_update(args):
@@ -691,12 +698,29 @@ def main():
     p_sankey.add_argument("--no-open", action="store_true",
                           help="Don't open browser automatically (html only)")
 
-    p_serve = sub.add_parser("serve",
-                              help="Start a prediction HTTP server")
+    p_serve = sub.add_parser(
+        "serve",
+        help="Start a prediction HTTP server (loopback by default, no auth)",
+    )
     p_serve.add_argument("artifact_dir", nargs="?", default=".tracer",
                          help="Artifact directory (default: .tracer)")
-    p_serve.add_argument("--host", default="0.0.0.0", help="Bind address (default: 0.0.0.0)")
+    p_serve.add_argument(
+        "--host", default="127.0.0.1",
+        help="Bind address (default: 127.0.0.1; use 0.0.0.0 only behind a reverse proxy)",
+    )
     p_serve.add_argument("--port", type=int, default=8000, help="Port (default: 8000)")
+    p_serve.add_argument(
+        "--cors-origin", default=None,
+        help="If set, emit Access-Control-Allow-Origin (e.g. https://app.example.com or *). Off by default.",
+    )
+    p_serve.add_argument(
+        "--max-body-bytes", type=int, default=16 * 1024 * 1024,
+        help="Reject request bodies larger than this (default: 16MiB)",
+    )
+    p_serve.add_argument(
+        "--max-batch", type=int, default=10_000,
+        help="Reject /predict_batch with more rows than this (default: 10000)",
+    )
 
     p_update = sub.add_parser("update",
                                help="Refit with new traces (continual learning)")