fix(webhook): skip preview deployments for fork PRs when public previews are off

app/Http/Controllers/Webhook/Github.php

@@ -62,6 +62,7 @@ class Github extends Controller
                 $before_sha = data_get($payload, 'before');
                 $after_sha = data_get($payload, 'after', data_get($payload, 'pull_request.head.sha'));
                 $author_association = data_get($payload, 'pull_request.author_association');
+                $is_fork_pull_request = $this->isForkPullRequest($payload);
             }
             if (! in_array($x_github_event, ['push', 'pull_request'])) {
                 return response("Nothing to do. Event '$x_github_event' is not supported.");
@@ -222,6 +223,7 @@ class Github extends Controller
                             commitSha: data_get($payload, 'pull_request.head.sha', 'HEAD'),
                             authorAssociation: $author_association,
                             fullName: $full_name,
+                            isForkPullRequest: $is_fork_pull_request ?? false,
                         );
 
                         $return_payloads->push([
@@ -303,6 +305,7 @@ class Github extends Controller
                 $before_sha = data_get($payload, 'before');
                 $after_sha = data_get($payload, 'after', data_get($payload, 'pull_request.head.sha'));
                 $author_association = data_get($payload, 'pull_request.author_association');
+                $is_fork_pull_request = $this->isForkPullRequest($payload);
             }
             if (! in_array($x_github_event, ['push', 'pull_request'])) {
                 return response("Nothing to do. Event '$x_github_event' is not supported.");
@@ -434,6 +437,7 @@ class Github extends Controller
                             commitSha: data_get($payload, 'pull_request.head.sha', 'HEAD'),
                             authorAssociation: $author_association,
                             fullName: $full_name,
+                            isForkPullRequest: $is_fork_pull_request ?? false,
                         );
 
                         $return_payloads->push([
@@ -451,6 +455,40 @@ class Github extends Controller
         }
     }
 
+    /**
+     * Determine whether a pull_request webhook payload originates from a fork.
+     *
+     * GitHub's `author_association` is not a reliable trust signal (it grants
+     * CONTRIBUTOR to anyone who has merely opened an issue/PR before), so fork
+     * detection is gated on whether the PR crosses repository boundaries.
+     *
+     * The repository id comparison is the canonical signal; the `head.repo.fork`
+     * flag and a case-insensitive full_name comparison are fallbacks for payloads
+     * where the ids are unavailable (e.g. a deleted head repository).
+     */
+    private function isForkPullRequest(mixed $payload): bool
+    {
+        $headRepoId = data_get($payload, 'pull_request.head.repo.id');
+        $baseRepoId = data_get($payload, 'pull_request.base.repo.id');
+
+        if ($headRepoId !== null && $baseRepoId !== null) {
+            return (string) $headRepoId !== (string) $baseRepoId;
+        }
+
+        if (data_get($payload, 'pull_request.head.repo.fork') === true) {
+            return true;
+        }
+
+        $headRepoFullName = data_get($payload, 'pull_request.head.repo.full_name');
+        $baseRepoFullName = data_get($payload, 'pull_request.base.repo.full_name');
+
+        if (is_string($headRepoFullName) && is_string($baseRepoFullName)) {
+            return Str::lower($headRepoFullName) !== Str::lower($baseRepoFullName);
+        }
+
+        return false;
+    }
+
     public function redirect(Request $request)
     {
         $code = (string) $request->query('code', '');

app/Jobs/ProcessGithubPullRequestWebhook.php

@@ -39,6 +39,7 @@ class ProcessGithubPullRequestWebhook implements ShouldBeEncrypted, ShouldQueue
         public string $commitSha,
         public ?string $authorAssociation,
         public string $fullName,
+        public bool $isForkPullRequest = false,
     ) {
         $this->onQueue('high');
     }
@@ -92,7 +93,17 @@ class ProcessGithubPullRequestWebhook implements ShouldBeEncrypted, ShouldQueue
 
         // Check if PR deployments from public contributors are restricted
         if (! $application->settings->is_pr_deployments_public_enabled) {
-            $trustedAssociations = ['OWNER', 'MEMBER', 'COLLABORATOR', 'CONTRIBUTOR'];
+            // Fork PRs carry untrusted code from a repository outside our control.
+            // GitHub's author_association cannot be trusted to gate these (it grants
+            // CONTRIBUTOR to anyone who has merely opened an issue/PR before), so fork
+            // PRs are never deployed automatically when public previews are off.
+            if ($this->isForkPullRequest) {
+                return;
+            }
+
+            // Same-repo (non-fork) branch PRs require push access to the base repo,
+            // so only trusted associations are allowed to trigger a deployment.
+            $trustedAssociations = ['OWNER', 'MEMBER', 'COLLABORATOR'];
             if (! in_array($this->authorAssociation, $trustedAssociations)) {
                 return;
             }

resources/views/livewire/project/application/advanced.blade.php

@@ -41,7 +41,7 @@
                     instantSave id="isPreviewDeploymentsEnabled" label="Preview Deployments" canGate="update"
                     :canResource="$application" />
                 <x-forms.checkbox
-                    helper="When enabled, anyone can trigger PR deployments. When disabled, only repository members, collaborators, and contributors can trigger PR deployments."
+                    helper="When enabled, anyone can trigger PR deployments. When disabled, fork PRs are blocked and only repository owners, members, and collaborators can trigger PR deployments."
                     instantSave id="isPrDeploymentsPublicEnabled" label="Allow Public PR Deployments" canGate="update"
                     :canResource="$application" :disabled="!$isPreviewDeploymentsEnabled" />