diff --git a/src/app/runtime-config-script.js b/src/app/runtime-config-script.js
index 0391f19..2a042fd 100644
--- a/src/app/runtime-config-script.js
+++ b/src/app/runtime-config-script.js
@@ -1,12 +1,18 @@
+import { headers } from 'next/headers';
 import { getAnglesApiUrl, RUNTIME_CONFIG_GLOBAL } from '../utils/runtime-config';
 
 // Server component. Rendered before any client code runs so that
 // `window.__ANGLES_CONFIG__` is populated by the time modules that read it
 // (e.g. the axios base URL in Shell.js) execute.
-export default function RuntimeConfigScript() {
+//
+// Carries the request's CSP nonce (set by src/proxy.js); without it the policy blocks
+// this inline script like any other.
+export default async function RuntimeConfigScript() {
     const config = { anglesApiUrl: getAnglesApiUrl() };
+    const nonce = (await headers()).get('x-nonce') || undefined;
     return (
         <script
+            nonce={nonce}
             // eslint-disable-next-line react/no-danger
             dangerouslySetInnerHTML={{
                 __html: `window.${RUNTIME_CONFIG_GLOBAL}=${JSON.stringify(config).replace(/</g, '\\u003c')};`,
diff --git a/src/components/features/execution-timeline/StepsTimeline.js b/src/components/features/execution-timeline/StepsTimeline.js
index ff9b4fb..8084603 100644
--- a/src/components/features/execution-timeline/StepsTimeline.js
+++ b/src/components/features/execution-timeline/StepsTimeline.js
@@ -1,7 +1,5 @@
 /* eslint react/no-array-index-key: [0] */
 import React from 'react';
-import DomPurify from 'dompurify';
-import parse from 'html-react-parser';
 import Moment from 'react-moment';
 
 import {
@@ -50,12 +48,19 @@ const StepsTimeline = function (props) {
     }
   };
 
-  const convertTextToLinks = (content) => {
-    const reg = /(http:\/\/|https:\/\/)((\w|=|\?|\.|\/|#|&|%|\+|-)+)/g;
-    if (content) {
-      return content.replace(reg, "<a href='$1$2' target='_blank'>$1$2</a>");
-    }
-    return '';
+  // Step info comes from test results, i.e. from anyone with an API token for the team, so
+  // it is rendered as text: HTML in it is shown, never interpreted. (It used to be parsed
+  // as HTML after DOMPurify, which still let through forms, inline styles and off-site
+  // links - enough for a convincing fake "session expired" form.) Only http(s) URLs are
+  // turned into links, built as React elements rather than markup.
+  const URL_PATTERN = /(https?:\/\/[\w=?./#&%+:~@,;!*'()$-]+)/g;
+  const renderInfo = (content) => {
+    if (!content) return '';
+    return String(content).split(URL_PATTERN).map((part, index) => (
+      index % 2 === 1 ? (
+        <a key={`${index}-${part}`} href={part} target="_blank" rel="noopener noreferrer">{part}</a>
+      ) : part
+    ));
   };
 
   const renderScreenshot = (step) => {
@@ -111,7 +116,7 @@ const StepsTimeline = function (props) {
           <Moment utc format="HH:mm:ss">{step.timestamp}</Moment>
         </span>
         <span className="step-name step-name-info">
-          {parse(DomPurify.sanitize(convertTextToLinks(step.info)))}
+          {renderInfo(step.info)}
         </span>
       </div>
     );
diff --git a/src/proxy.js b/src/proxy.js
new file mode 100644
index 0000000..81e077c
--- /dev/null
+++ b/src/proxy.js
@@ -0,0 +1,80 @@
+import { NextResponse } from 'next/server';
+import { getAnglesApiBaseUrl } from './utils/runtime-config';
+
+/*
+ * Security headers for every page.
+ *
+ * - Content-Security-Policy with a per-request nonce. Next.js reads the nonce from the
+ *   request's CSP header and puts it on its own scripts; RuntimeConfigScript reads it from
+ *   `x-nonce`. Scripts without it - anything injected into a page - do not run.
+ * - `frame-ancestors 'none'` and X-Frame-Options: the UI cannot be framed by another site,
+ *   so it cannot be used for clickjacking.
+ * - `form-action 'self'`: a form can only submit to the UI itself, never off-site.
+ *
+ * The API is on another origin in most deployments and its URL is only known at runtime
+ * (ANGLES_API_BASE_URL), which is why this is built per request here rather than as a
+ * static header in next.config.mjs.
+ */
+
+// The origin (scheme, host and port) of a configured URL, or undefined if it is not one.
+const originOf = (url) => {
+  try {
+    return new URL(url).origin;
+  } catch (error) {
+    return undefined;
+  }
+};
+
+export const buildContentSecurityPolicy = (nonce, apiOrigin, isDev) => {
+  const connect = ["'self'", apiOrigin].filter(Boolean).join(' ');
+  return [
+    "default-src 'self'",
+    // 'strict-dynamic' lets the nonced Next.js runtime load the page's other chunks. In
+    // development React needs eval for its error overlays; production does not.
+    `script-src 'self' 'nonce-${nonce}' 'strict-dynamic'${isDev ? " 'unsafe-eval'" : ''}`,
+    // rsuite and ApexCharts set inline styles at runtime, which a nonce cannot cover.
+    "style-src 'self' 'unsafe-inline'",
+    // Screenshots arrive as data: URIs; attachments are shown from blob: URLs.
+    "img-src 'self' data: blob:",
+    "media-src 'self' blob:",
+    "font-src 'self' data:",
+    `connect-src ${connect}`,
+    // HTML snapshots are shown in a srcdoc iframe, which inherits this policy.
+    "frame-src 'self'",
+    "object-src 'none'",
+    "base-uri 'self'",
+    "form-action 'self'",
+    "frame-ancestors 'none'",
+  ].join('; ');
+};
+
+export function proxy(request) {
+  const nonce = Buffer.from(crypto.randomUUID()).toString('base64');
+  const isDev = process.env.NODE_ENV === 'development';
+  const csp = buildContentSecurityPolicy(nonce, originOf(getAnglesApiBaseUrl()), isDev);
+
+  const requestHeaders = new Headers(request.headers);
+  requestHeaders.set('x-nonce', nonce);
+  requestHeaders.set('Content-Security-Policy', csp);
+
+  const response = NextResponse.next({ request: { headers: requestHeaders } });
+  response.headers.set('Content-Security-Policy', csp);
+  // For browsers that predate frame-ancestors.
+  response.headers.set('X-Frame-Options', 'DENY');
+  response.headers.set('X-Content-Type-Options', 'nosniff');
+  response.headers.set('Referrer-Policy', 'strict-origin-when-cross-origin');
+  return response;
+}
+
+export const config = {
+  matcher: [
+    {
+      // Pages only: static chunks, images and public assets need no policy.
+      source: '/((?!_next/static|_next/image|favicon.png|assets/|manifest.json|robots.txt).*)',
+      missing: [
+        { type: 'header', key: 'next-router-prefetch' },
+        { type: 'header', key: 'purpose', value: 'prefetch' },
+      ],
+    },
+  ],
+};