diff --git a/CHANGELOG.md b/CHANGELOG.md
index 55aa99b..d47354b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,28 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.3.4] - 2026-09-30
+
+### Security
+
+- **Custom SVG icons can no longer load external URLs** - a crafted icon could
+  hide an off-site `url(...)` in its `style` or paint attributes by putting a
+  quote or `)` inside the URL, which slipped past the sanitizer. Opening a map
+  that used such an icon made the browser contact the attacker's server,
+  revealing your IP address and when you opened it. No script could run. The
+  check now rejects anything but plain same-icon `url(#id)` references, and
+  icons already saved in the browser are cleaned the next time NetGraph loads.
+- **Added a Content Security Policy** - as a second line of defense, the page
+  (and the offline copy) now tells the browser it may not load images, scripts
+  or anything else from another site, or send data anywhere. Even if a crafted
+  map or icon ever slipped past the sanitizer again, it could not contact an
+  outside server.
+
+### Changed
+
+- **Updated the Lucide icon set** - `lucide-static` 1.46.0 -> 1.47.0. None of
+  the icons NetGraph ships changed, so maps look exactly the same.
+
 ## [1.3.3] - 2026-09-15
 
 ### Changed
@@ -115,7 +137,8 @@ describes the app as it stands at that release.
 - **Touch support** - drag to pan, pinch to zoom, and long-press for context
   menus on tablets.
 
-[Unreleased]: https://github.com/BrainInBlack/NetGraph/compare/v1.3.3...HEAD
+[Unreleased]: https://github.com/BrainInBlack/NetGraph/compare/v1.3.4...HEAD
+[1.3.4]: https://github.com/BrainInBlack/NetGraph/compare/v1.3.3...v1.3.4
 [1.3.3]: https://github.com/BrainInBlack/NetGraph/compare/v1.3.2...v1.3.3
 [1.3.2]: https://github.com/BrainInBlack/NetGraph/compare/v1.3.1...v1.3.2
 [1.3.1]: https://github.com/BrainInBlack/NetGraph/compare/v1.3.0...v1.3.1
diff --git a/index.html b/index.html
index 69a9b4f..2fe8103 100644
--- a/index.html
+++ b/index.html
@@ -2,6 +2,16 @@
 <html lang="en">
   <head>
     <meta charset="UTF-8" />
+    <!-- Content Security Policy - defense-in-depth behind the SVG sanitizer and
+         escapeHtml: nothing may load from or talk to another origin.
+         - style-src needs 'unsafe-inline': cards, panels and custom icons carry
+           style="" attributes set via innerHTML.
+         - img-src data:/blob: - raster custom icons are data: URLs; the upload
+           path decodes files through a blob: object URL.
+         - The single-file build (dist/download/netgraph.html) inlines its JS;
+           vite.config.ts cspInlineScriptHashes() appends that script's sha256
+           to script-src at build time, so keep script-src as exactly 'self'. -->
+    <meta http-equiv="Content-Security-Policy" content="default-src 'none'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob:; connect-src 'self'; base-uri 'none'; form-action 'none'" />
     <link rel="icon" type="image/svg+xml" href="./src/assets/favicon.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>NetGraph</title>
diff --git a/package-lock.json b/package-lock.json
index 6a9fc5e..d88b6f1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "netgraph",
-  "version": "1.3.3",
+  "version": "1.3.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "netgraph",
-      "version": "1.3.3",
+      "version": "1.3.4",
       "license": "SEE LICENSE IN LICENSE",
       "dependencies": {
         "lucide-static": "^1.47.0"
diff --git a/package.json b/package.json
index 661bbea..8fcde51 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "netgraph",
   "private": true,
-  "version": "1.3.3",
+  "version": "1.3.4",
   "description": "Browser-based local network visualizer - map your home or lab network, stored entirely in localStorage with no backend.",
   "license": "SEE LICENSE IN LICENSE",
   "author": "BrainInBlack <braininblack@gmail.com>",
diff --git a/src/ts/svg-sanitizer.test.ts b/src/ts/svg-sanitizer.test.ts
index b24e0f2..4159d08 100644
--- a/src/ts/svg-sanitizer.test.ts
+++ b/src/ts/svg-sanitizer.test.ts
@@ -318,6 +318,38 @@ describe('sanitizeSvg - url() filter bypasses', () => {
     expect(out!).not.toMatch(/evil/);
   });
 
+  // A quoted URL containing `'`, `"` or `)` is still a valid url() to CSS, but
+  // defeated the old "extract the target" regex - it matched nothing and the
+  // value passed. The root <svg>'s background fetches on render (beacon).
+  it.each([
+    ['single quote', `<svg xmlns="http://www.w3.org/2000/svg" style="background:url(&quot;http://evil/b?a='&quot;)"/>`],
+    ['double quote', `<svg xmlns="http://www.w3.org/2000/svg" style='background:url("http://evil/b?a=&quot;")'/>`],
+    ['close paren', `<svg xmlns="http://www.w3.org/2000/svg" style='background-image:url("http://evil/b?)")'/>`],
+  ])('drops style with an off-document url() holding a %s', (_label, svg) => {
+    const out = sanitizeSvg(svg);
+    expect(out!).not.toMatch(/style=/);
+    expect(out!).not.toMatch(/evil/);
+  });
+
+  it('drops fill with an off-document url() holding a close paren', () => {
+    const out = sanitizeSvg(wrap(`<rect fill='url("http://evil/a.svg?)#m")'/>`));
+    expect(out!).not.toMatch(/fill=/);
+    expect(out!).not.toMatch(/evil/);
+  });
+
+  it('drops a fragment url() whose id holds characters outside the id set', () => {
+    const out = sanitizeSvg(wrap(`<rect fill="url('#a)b')"/>`));
+    expect(out!).not.toMatch(/fill=/);
+  });
+
+  it('keeps quoted fragment url() refs', () => {
+    const out = sanitizeSvg(wrap(
+      `<defs><linearGradient id="g"/><mask id="m"/></defs><rect style="fill:url('#g');mask:url(&quot;#m&quot;)"/>`
+    ));
+    expect(out!).toMatch(/style="[^"]*url\('#g'\)/);
+    expect(out!).toMatch(/url\(&quot;#m&quot;\)/);
+  });
+
   it('still keeps a clean style with only fragment url() refs', () => {
     const out = sanitizeSvg(wrap(
       '<defs><linearGradient id="g"/></defs><rect style="fill:url(#g);opacity:0.5"/>'
diff --git a/src/ts/svg-sanitizer.ts b/src/ts/svg-sanitizer.ts
index 938b7cd..48f6ab7 100644
--- a/src/ts/svg-sanitizer.ts
+++ b/src/ts/svg-sanitizer.ts
@@ -162,11 +162,13 @@ function areAllUrlsFragmentRefs(value: string): boolean {
   if (/\\/.test(value)) return false;
   if (/(?:image-set|image|cross-fade|element)\s*\(/i.test(value)) return false;
 
-  const URL_TOKEN = /url\(\s*(['"]?)([^'")]*)\1\s*\)/gi;
-  let match: RegExpExecArray | null;
-  while ((match = URL_TOKEN.exec(value)) !== null) {
-    const target = match[2].trim();
-    if (!target.startsWith('#')) return false;
-  }
-  return true;
+  // Fail closed: count every `url(` opener, then count only the strict
+  // fragment-ref forms. Any opener the strict pattern can't account for -
+  // e.g. a quoted URL holding `'`, `"` or `)`, which a looser "extract the
+  // target" regex silently fails to match - makes the counts differ and the
+  // value is rejected.
+  const openers = value.match(/url\s*\(/gi)?.length ?? 0;
+  const fragmentRefs =
+    value.match(/url\(\s*(['"]?)#[a-zA-Z0-9_\-:.]+\1\s*\)/gi)?.length ?? 0;
+  return openers === fragmentRefs;
 }
diff --git a/vite.config.ts b/vite.config.ts
index e17602c..97cc6da 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -3,6 +3,7 @@ import { viteSingleFile } from 'vite-plugin-singlefile';
 import { renameSync } from 'node:fs';
 import { join } from 'node:path';
 import { createRequire } from 'node:module';
+import { createHash } from 'node:crypto';
 
 const { version: appVersion } = createRequire(import.meta.url)('./package.json') as { version: string };
 
@@ -40,6 +41,40 @@ function inlineFavicon() {
   };
 }
 
+/**
+ * Allow the single-file build's inlined script under the CSP in index.html.
+ * vite-plugin-singlefile turns `<script src>` into an inline `<script>`, which
+ * `script-src 'self'` blocks - so hash every inline script body and append the
+ * `'sha256-...'` sources to script-src (keeps 'unsafe-inline' out of the
+ * policy). Runs in the `post` generateBundle phase, after singlefile inlined
+ * and minified the code, so the hash covers the exact shipped bytes. Fails the
+ * build if the CSP marker is missing rather than shipping a page that won't run.
+ */
+function cspInlineScriptHashes() {
+  return {
+    name: 'csp-inline-script-hashes',
+    enforce: 'post' as const,
+    generateBundle: {
+      order: 'post' as const,
+      handler(_opts: unknown, bundle: Record<string, { fileName: string; source?: string | Uint8Array }>) {
+        const html = Object.values(bundle).find(b => b.fileName === 'index.html');
+        if (!html || typeof html.source !== 'string') return;
+        const hashes = [...html.source.matchAll(/<script\b[^>]*>([\s\S]*?)<\/script>/g)]
+          .map(m => m[1])
+          .filter(body => body.length > 0)
+          .map(body => `'sha256-${createHash('sha256').update(body, 'utf8').digest('base64')}'`);
+        // Anchored to the CSP meta's content attribute, so a mention of the
+        // directive elsewhere (e.g. an HTML comment) can't take the hashes.
+        const CSP_SCRIPT_SRC = /(http-equiv="Content-Security-Policy"\s+content="[^"]*?script-src 'self')/;
+        if (!CSP_SCRIPT_SRC.test(html.source)) {
+          throw new Error("csp-inline-script-hashes: no \"script-src 'self'\" in the index.html CSP meta");
+        }
+        html.source = html.source.replace(CSP_SCRIPT_SRC, `$1 ${hashes.join(' ')}`);
+      },
+    },
+  };
+}
+
 /**
  * Rename the emitted HTML file on disk. Vite names the single-file output
  * `index.html` (after its `index.html` entry); we want it served as
@@ -76,7 +111,9 @@ export default defineConfig(({ mode, command }) => {
       // download/netgraph.html actually exists.
       __WEB_BUILD__: JSON.stringify(command === 'build' && !single),
     },
-    plugins: single ? [viteSingleFile(), inlineFavicon(), renameHtml('netgraph.html')] : [],
+    plugins: single
+      ? [viteSingleFile(), inlineFavicon(), cspInlineScriptHashes(), renameHtml('netgraph.html')]
+      : [],
     build: {
       outDir: single ? 'dist/download' : 'dist',
       emptyOutDir: true,