diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..455a07b
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,25 @@
+version: 2
+updates:
+  # VS Code extension JavaScript/TypeScript toolchain.
+  - package-ecosystem: npm
+    directory: /vscode-extension
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    groups:
+      dev-dependencies:
+        dependency-type: development
+
+  # Python build-time deps used by the keyword-index generator.
+  - package-ecosystem: pip
+    directory: /scripts
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 3
+
+  # CI actions — keep SHA pins fresh as upstream tags advance.
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
diff --git a/.github/workflows/build-vsix.yml b/.github/workflows/build-vsix.yml
index 102ad8e..2044770 100644
--- a/.github/workflows/build-vsix.yml
+++ b/.github/workflows/build-vsix.yml
@@ -8,17 +8,21 @@ on:
     branches: [main]
   workflow_dispatch:
 
+# Default least-privilege token scope; jobs that need more elevate explicitly.
+permissions:
+  contents: read
+
 jobs:
   build-index:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout (with submodule)
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6
         with:
           submodules: recursive
 
       - name: Setup Python
-        uses: actions/setup-python@v6
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405  # v6
         with:
           python-version: '3.12'
           cache: pip
@@ -39,7 +43,7 @@ jobs:
             --compact vscode-extension/data/keyword_index_compact.json
 
       - name: Upload keyword index
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7
         with:
           name: keyword-index
           path: vscode-extension/data/keyword_index_compact.json
@@ -56,17 +60,17 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6
 
       - name: Setup Node.js
-        uses: actions/setup-node@v6
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e  # v6
         with:
           node-version: '24'
           cache: npm
           cache-dependency-path: vscode-extension/package-lock.json
 
       - name: Download freshly built keyword index
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8
         with:
           name: keyword-index
           path: vscode-extension/data
@@ -81,10 +85,10 @@ jobs:
         run: npm run compile
 
       - name: Package VSIX
-        run: npx --yes @vscode/vsce package
+        run: npx --yes @vscode/vsce@3.9.1 package
 
       - name: Upload VSIX artifact
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7
         with:
           name: opm-flow-editor-support-vsix
           path: vscode-extension/opm-flow-editor-support-*.vsix
@@ -92,7 +96,7 @@ jobs:
 
       - name: Attach VSIX to release
         if: startsWith(github.ref, 'refs/tags/v')
-        uses: softprops/action-gh-release@v3
+        uses: softprops/action-gh-release@b4309332981a82ec1c5618f44dd2e27cc8bfbfda  # v3
         with:
           files: vscode-extension/opm-flow-editor-support-*.vsix
 
@@ -102,12 +106,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Setup Node.js
-        uses: actions/setup-node@v6
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e  # v6
         with:
           node-version: '24'
 
       - name: Download VSIX
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8
         with:
           name: opm-flow-editor-support-vsix
           path: .
@@ -115,7 +119,7 @@ jobs:
       - name: Publish to VS Code Marketplace
         env:
           VSCE_PAT: ${{ secrets.VSCE_PAT }}
-        run: npx --yes @vscode/vsce publish --packagePath opm-flow-editor-support-*.vsix --pat "$VSCE_PAT"
+        run: npx --yes @vscode/vsce@3.9.1 publish --packagePath opm-flow-editor-support-*.vsix --pat "$VSCE_PAT"
 
   # Disabled until Open VSX account + OVSX_PAT secret are set up.
   # To re-enable: change `if: false` back to `if: startsWith(github.ref, 'refs/tags/v')`.
@@ -125,12 +129,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Setup Node.js
-        uses: actions/setup-node@v6
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e  # v6
         with:
           node-version: '24'
 
       - name: Download VSIX
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8
         with:
           name: opm-flow-editor-support-vsix
           path: .
@@ -138,4 +142,4 @@ jobs:
       - name: Publish to Open VSX
         env:
           OVSX_PAT: ${{ secrets.OVSX_PAT }}
-        run: npx --yes ovsx publish opm-flow-editor-support-*.vsix -p "$OVSX_PAT"
+        run: npx --yes ovsx@0.10.12 publish opm-flow-editor-support-*.vsix -p "$OVSX_PAT"
diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000..0ff369c
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,42 @@
+# Security Policy
+
+## Supported versions
+
+Only the latest released version of the OPM Flow Editor Support VS Code
+extension receives security updates. Older versions are not patched.
+
+## Reporting a vulnerability
+
+If you believe you have found a security vulnerability in this extension,
+please report it privately rather than opening a public issue.
+
+Use GitHub's
+[private vulnerability reporting](https://github.com/OPM/opm-flow-editor-support/security/advisories/new)
+to route the report directly to the maintainers. Please include:
+
+- A description of the issue and its impact.
+- Steps to reproduce, ideally including a minimal deck file or
+  configuration that triggers the behaviour.
+- The extension version (`Extensions: Show Installed Extensions` in
+  VS Code) and your VS Code version.
+
+You should receive an acknowledgement within a few business days. We will
+work with you on a fix and coordinate a disclosure timeline; please give
+us a reasonable window to release a patched version before any public
+disclosure.
+
+## Scope
+
+In scope:
+
+- The published `magne-sjaastad.opm-flow-editor-support` VS Code extension.
+- The build / packaging pipeline in `.github/workflows/build-vsix.yml`.
+- Helper scripts in `scripts/` that produce the bundled keyword index.
+
+Out of scope:
+
+- Vulnerabilities in OPM Flow itself, the OPM reference manual, or other
+  upstream OPM projects — please report those to the relevant
+  [OPM repository](https://github.com/OPM).
+- Issues that require an already-compromised developer machine or an
+  attacker-controlled VS Code installation.
diff --git a/vscode-extension/src/extension.ts b/vscode-extension/src/extension.ts
index 993af1c..3e23c48 100644
--- a/vscode-extension/src/extension.ts
+++ b/vscode-extension/src/extension.ts
@@ -200,7 +200,12 @@ function resolveKeyword(index: KeywordIndex, kw: string): KeywordEntry | undefin
 // ---------------------------------------------------------------------------
 
 function escHtml(s: string): string {
-  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
+  return s
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&#39;');
 }
 
 function paramTypeLabel(p: Parameter): string {
@@ -327,7 +332,7 @@ function buildDocsHtml(
         ? ' class="highlight"' : '';
       const dataRecord = p.record !== undefined
         ? ` data-record="${escHtml(String(p.record))}"` : '';
-      return `<tr data-param-index="${escHtml(String(p.index))}"${dataRecord}${hl}><td>${p.index}</td><td class="name"><code>${escHtml(p.name)}</code></td><td>${escHtml(p.description)}</td>${typeCell}${unitCells}${defaultCell}</tr>`;
+      return `<tr data-param-index="${escHtml(String(p.index))}"${dataRecord}${hl}><td>${escHtml(String(p.index))}</td><td class="name"><code>${escHtml(p.name)}</code></td><td>${escHtml(p.description)}</td>${typeCell}${unitCells}${defaultCell}</tr>`;
     };
 
     const tableHead = `<thead><tr><th>No.</th><th class="name">Name</th><th>Description</th>${typeCol}${unitCols}${defaultCol}</tr></thead>`;
@@ -422,7 +427,10 @@ class DocsViewProvider implements vscode.WebviewViewProvider {
 
   resolveWebviewView(view: vscode.WebviewView): void {
     this._view = view;
-    view.webview.options = { enableScripts: true };
+    // The docs panel renders only inline HTML/CSS/JS that we build here, so
+    // it never needs to load files from disk. Drop `localResourceRoots` to
+    // an empty list to deny the webview any filesystem access.
+    view.webview.options = { enableScripts: true, localResourceRoots: [] };
     view.webview.html = buildDocsHtml(null, null, getDocColumns());
     this._currentEntry = undefined;
     this._currentParam = undefined;
@@ -469,7 +477,9 @@ function buildKeywordHover(
   isExcluded?: boolean,
 ): vscode.MarkdownString {
   const md = new vscode.MarkdownString();
-  md.isTrusted = true;
+  // `supportHtml` is enough for the inline <span style="..."> notices below.
+  // `isTrusted` would additionally permit `command:` links to execute, which
+  // these hovers never use — keep it off as defense in depth.
   md.supportHtml = true;
 
   if (
@@ -499,7 +509,7 @@ function buildKeywordHover(
 
 function buildParameterHover(entry: KeywordEntry, param: Parameter): vscode.MarkdownString {
   const md = new vscode.MarkdownString();
-  md.isTrusted = true;
+  // No HTML or command links needed here — pure markdown is sufficient.
   md.appendMarkdown(`**\`${entry.name}\` — parameter ${param.index}: \`${param.name}\`**\n\n`);
   md.appendMarkdown(`${param.description}\n\n`);
   const cols = getDocColumns();