diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index af64181..dbe2465 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,7 +20,7 @@ jobs:
 
     steps:
       - name: Check out repository
-        uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
 
@@ -61,6 +61,7 @@ jobs:
         run: |
           npm install --prefix "$RUNNER_TEMP/acp-browser" --no-save --ignore-scripts playwright@1.63.0 jquery@3.7.1
           "$RUNNER_TEMP/acp-browser/node_modules/.bin/playwright" install --with-deps chromium
+          ACP_BROWSER_MODULES="$RUNNER_TEMP/acp-browser/node_modules" node tests/browser_fixture_test.cjs
           ACP_BROWSER_MODULES="$RUNNER_TEMP/acp-browser/node_modules" node tests/theme_ui.cjs
           ACP_BROWSER_MODULES="$RUNNER_TEMP/acp-browser/node_modules" node tests/maintenance_ui.cjs
 
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 8aa06ab..cceddf4 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Check out repository
-        uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
 
diff --git a/.github/workflows/pr-test-package.yml b/.github/workflows/pr-test-package.yml
index f1750f1..ee4f9e5 100644
--- a/.github/workflows/pr-test-package.yml
+++ b/.github/workflows/pr-test-package.yml
@@ -18,7 +18,7 @@ jobs:
     if: github.event.label.name == 'test-build'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           persist-credentials: false
diff --git a/.github/workflows/validate-workflows.yml b/.github/workflows/validate-workflows.yml
index 0b0cc02..a0139eb 100644
--- a/.github/workflows/validate-workflows.yml
+++ b/.github/workflows/validate-workflows.yml
@@ -15,7 +15,7 @@ jobs:
   actionlint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
       - name: Install verified actionlint
diff --git a/tests/browser_fixture.cjs b/tests/browser_fixture.cjs
new file mode 100644
index 0000000..770d3bc
--- /dev/null
+++ b/tests/browser_fixture.cjs
@@ -0,0 +1,12 @@
+// Prepare trusted repository fixtures, not arbitrary/untrusted HTML. Preserve
+// inline configuration while loading external scripts and styles explicitly.
+async function setFixtureContent(page, html) {
+  const documentHtml = await page.evaluate(markup => {
+    const doc = new DOMParser().parseFromString(markup, 'text/html');
+    doc.querySelectorAll('script[src], link').forEach(element => element.remove());
+    return '<!DOCTYPE html>' + doc.documentElement.outerHTML;
+  }, html);
+  await page.setContent(documentHtml);
+}
+
+module.exports = {setFixtureContent};
diff --git a/tests/browser_fixture_test.cjs b/tests/browser_fixture_test.cjs
new file mode 100644
index 0000000..9e645dd
--- /dev/null
+++ b/tests/browser_fixture_test.cjs
@@ -0,0 +1,26 @@
+const assert = require('node:assert/strict');
+const path = require('node:path');
+const dependency = name => process.env.ACP_BROWSER_MODULES ? path.join(process.env.ACP_BROWSER_MODULES, name) : name;
+const {chromium} = require(dependency('playwright'));
+const {setFixtureContent} = require('./browser_fixture.cjs');
+
+(async () => {
+  const browser = await chromium.launch({headless:true});
+  try {
+    const page = await browser.newPage();
+    const requests = [];
+    await page.route('**/*', route => { requests.push(route.request().url()); return route.abort(); });
+    await setFixtureContent(page, `<!doctype html><html lang="en"><head>
+      <SCRIPT defer SRC='https://fixture.invalid/one.js'></SCRIPT >
+      <script src=https://fixture.invalid/two.js></script\n>
+      <LiNk rel=stylesheet href='https://fixture.invalid/style.css'>
+      <script>window.fixtureConfig = {value: 'inline configuration retained'};</script>
+      </head><body><main id="fixture">Fixture content</main></body></html>`);
+    assert.equal(await page.locator('script[src], link').count(), 0);
+    assert.equal(await page.evaluate(() => window.fixtureConfig.value), 'inline configuration retained');
+    assert.equal(await page.locator('#fixture').textContent(), 'Fixture content');
+    assert.equal(await page.evaluate(() => document.compatMode), 'CSS1Compat');
+    assert.deepEqual(requests, [], 'Fixture assets must not be requested before explicit injection');
+    console.log('browser_fixture: DOM preparation handles alternate tag syntax and preserves inline configuration.');
+  } finally { await browser.close(); }
+})().catch(error => { console.error(error); process.exitCode = 1; });
diff --git a/tests/i18n_layout.cjs b/tests/i18n_layout.cjs
index 7a1d116..af0d1e6 100644
--- a/tests/i18n_layout.cjs
+++ b/tests/i18n_layout.cjs
@@ -3,6 +3,7 @@
 const path = require('node:path');
 const fs = require('node:fs');
 const {execFileSync} = require('node:child_process');
+const {setFixtureContent} = require('./browser_fixture.cjs');
 const assert = require('node:assert/strict');
 const modules = process.env.ACP_BROWSER_MODULES;
 const dependency = name => modules ? path.join(modules, name) : name;
@@ -15,13 +16,12 @@ const locales = JSON.parse(fs.readFileSync(path.join(plugin, 'locales/locales.js
   const browser = await chromium.launch({headless:true});
   try {
     for (const [locale, definition] of Object.entries(locales)) {
-      const html = execFileSync('php', [path.join(__dirname, 'render_i18n_page.php'), locale], {encoding:'utf8', maxBuffer:4e6})
-        .replace(/<script src="[^"]*"><\/script>/g, '').replace(/<link[^>]+>/g, '');
+      const html = execFileSync('php', [path.join(__dirname, 'render_i18n_page.php'), locale], {encoding:'utf8', maxBuffer:4e6});
       for (const width of [1280, 390]) {
         const page = await browser.newPage({viewport:{width, height:900}});
         const errors = [];
         page.on('pageerror', error => errors.push(error.message));
-        await page.setContent(html);
+        await setFixtureContent(page, html);
         await page.addStyleTag({path:path.join(plugin, 'styles/appdata.cleanup.plus.css')});
         await page.addScriptTag({path:jquery});
         for (const name of ['appdata.cleanup.plus.shared.js', 'appdata.cleanup.plus.panels.js']) {
diff --git a/tests/maintenance_ui.cjs b/tests/maintenance_ui.cjs
index 9dd8809..69d9ded 100644
--- a/tests/maintenance_ui.cjs
+++ b/tests/maintenance_ui.cjs
@@ -3,6 +3,7 @@ const fs = require('node:fs');
 const path = require('node:path');
 const assert = require('node:assert/strict');
 const {execFileSync} = require('node:child_process');
+const {setFixtureContent} = require('./browser_fixture.cjs');
 const modules = process.env.ACP_BROWSER_MODULES;
 const dependency = name => modules ? path.join(modules, name) : name;
 const {chromium} = require(dependency('playwright'));
@@ -13,8 +14,8 @@ const plugin = path.resolve(__dirname, '../source/appdata.cleanup.plus/usr/local
     const page = await browser.newPage({viewport:{width:1440,height:1000}});
     const errors = [];
     page.on('pageerror', e=>errors.push(e.message));
-    const html = execFileSync('php', [path.join(__dirname,'render_i18n_page.php'),'en_US'], {encoding:'utf8',maxBuffer:4e6}).replace(/<script src="[^"]*"><\/script>/g,'').replace(/<link[^>]+>/g,'');
-    await page.setContent(html);
+    const html = execFileSync('php', [path.join(__dirname,'render_i18n_page.php'),'en_US'], {encoding:'utf8',maxBuffer:4e6});
+    await setFixtureContent(page, html);
     await page.addStyleTag({path:path.join(plugin,'styles/appdata.cleanup.plus.css')});
     await page.addScriptTag({path:require.resolve(dependency('jquery/dist/jquery.js'))});
     await page.evaluate(() => {
diff --git a/tests/theme_ui.cjs b/tests/theme_ui.cjs
index bc7ff04..f7f22bf 100644
--- a/tests/theme_ui.cjs
+++ b/tests/theme_ui.cjs
@@ -4,6 +4,7 @@ const fs = require('node:fs');
 const path = require('node:path');
 const assert = require('node:assert/strict');
 const {execFileSync} = require('node:child_process');
+const {setFixtureContent} = require('./browser_fixture.cjs');
 const dependency = name => process.env.ACP_BROWSER_MODULES ? path.join(process.env.ACP_BROWSER_MODULES, name) : name;
 const {chromium} = require(dependency('playwright'));
 const plugin = path.resolve(__dirname, '../source/appdata.cleanup.plus/usr/local/emhttp/plugins/appdata.cleanup.plus');
@@ -32,8 +33,8 @@ async function nativeCss(version, theme) {
       const page = await browser.newPage({viewport:{width,height:1000}});
       const errors = [];
       page.on('pageerror',error=>errors.push(error.message));
-      const html = execFileSync('php',[path.join(__dirname,'render_i18n_page.php'),'en_US',theme],{encoding:'utf8',maxBuffer:4e6}).replace(/<script src="[^"]*"><\/script>/g,'').replace(/<link[^>]+>/g,'');
-      await page.setContent(html);
+      const html = execFileSync('php',[path.join(__dirname,'render_i18n_page.php'),'en_US',theme],{encoding:'utf8',maxBuffer:4e6});
+      await setFixtureContent(page, html);
       const hostStyle = await page.addStyleTag({content:await nativeCss(version,theme)});
       await hostStyle.evaluate(el=>el.id='native-theme');
       await page.addStyleTag({path:path.join(plugin,'styles/appdata.cleanup.plus.css')});