Fix open redirect in tag.php + language.php: reject protocol-relative URLs (//evil.com) by also checking for // prefix

TODO.md

@@ -1,9 +1,10 @@
 # TODO
 
 > Last updated: 2026-06-24
-> Context: Setup biome + rolldown + lightningcss build pipeline for JS/CSS bundling & minification
+> Context: Security audit — fix open redirects, fragment auth, dead code, CSRF gaps
 
 ## Completed
+- [x] #sec-open-redirect Fix open redirect in tag.php + language.php (protocol-relative URL bypass via str_starts_with) ✓
 - [x] #build-pipeline Setup biome + rolldown + lightningcss build pipeline ✓
   - [x] #build-packagejson Create package.json with devDependencies ✓
   - [x] #build-biomecss Update biome.json to handle CSS formatting ✓
@@ -15,6 +16,9 @@
   - [x] #build-cssfix Fix stray `}` syntax error in admin.css line 305 ✓
 
 ## Pending
+- [ ] #sec-fragments-auth Gate partagé fragments on share_active session + CSRF `(partage/fragments/*.php, partage/index.php)`
+- [ ] #sec-retry-csrf Add CSRF check to partage/retry-email.php POST
+- [ ] #sec-cleanup-dead-code Remove dead App::verifyCsrf() or refactor action handlers to use it
 - [ ] #rep-student-touch Replace hover student popover with tap-to-open drawer for mobile `(repertoire.php, repertoire.css)`
 - [ ] #rep-polish Polish: scroll-position memory on HTMX swap, animation tuning `(repertoire.css)`
 - [ ] #icon-color-verify Verify icon colors render correctly across all pages (header, admin tables, forms, dialogs, cleanup modal)

app/public/admin/actions/language.php

@@ -74,9 +74,10 @@ try {
 }
 
 $redirect = '/admin/contenus.php';
-// Allow the caller to override the redirect
-if (!empty($_POST['return']) && str_starts_with($_POST['return'], '/')) {
-    $redirect = $_POST['return'];
+// Allow the caller to override the redirect (same-origin only, no protocol-relative)
+$return = $_POST['return'] ?? '';
+if ($return !== '' && str_starts_with($return, '/') && !str_starts_with($return, '//')) {
+    $redirect = $return;
 }
 header('Location: ' . $redirect);
 exit();

app/public/admin/actions/tag.php

@@ -79,9 +79,10 @@ try {
 }
 
 $redirect = '/admin/tags.php';
-// Allow the caller to override the redirect
-if (!empty($_POST['return']) && str_starts_with($_POST['return'], '/')) {
-    $redirect = $_POST['return'];
+// Allow the caller to override the redirect (same-origin only, no protocol-relative)
+$return = $_POST['return'] ?? '';
+if ($return !== '' && str_starts_with($return, '/') && !str_starts_with($return, '//')) {
+    $redirect = $return;
 }
 header('Location: ' . $redirect);
 exit();