diff --git a/.docker/nginx/conf.d/default.conf b/.docker/nginx/conf.d/default.conf
index a53cff6eff..0dcc120116 100644
--- a/.docker/nginx/conf.d/default.conf
+++ b/.docker/nginx/conf.d/default.conf
@@ -17,6 +17,13 @@ server {
         try_files $uri $uri/ /index.php?$query_string;
     }
 
+    # File hasil upload disajikan langsung dari storage/app/public (symlink
+    # public/storage) sehingga tidak melewati aplikasi. Blokir eksekusi skrip
+    # di jalur ini sebagai lap keamanan terakhir.
+    location ~* ^/storage/.*\.(php|php[0-9]?|phtml|phar|pl|py|rb|sh|bash|cgi|jsp|asp|aspx|htaccess)$ {
+        deny all;
+    }
+
     error_page 404 /index.php;
 
     location ~ \.php$ {
diff --git a/app/Http/Middleware/SecurityHeaders.php b/app/Http/Middleware/SecurityHeaders.php
index c7441b2932..83ba878258 100644
--- a/app/Http/Middleware/SecurityHeaders.php
+++ b/app/Http/Middleware/SecurityHeaders.php
@@ -47,6 +47,17 @@ public function handle($request, Closure $next)
         /** @var \Illuminate\Http\Response $response */
         $response = $next($request);
 
+        foreach ($this->unwantedHeaders as $header) {
+            $response->headers->remove($header);
+        }
+
+        /*
+         * Cegah browser menebak-nebak Content-Type dari isi file. Tanpa header ini
+         * file markup seperti SVG dapat dieksekusi sebagai script meskipun
+         * header dan nama ekstensinya tidak menyerupai HTML.
+         */
+        $response->headers->set('X-Content-Type-Options', 'nosniff');
+
         if (app()->environment('production')) {
             $localDomain = env('APP_URL', 'http://localhost');
             $urlDatabaseGabungan = config('setting.api_server_database_gabungan');
diff --git a/app/Providers/AppServiceProvider.php b/app/Providers/AppServiceProvider.php
index a9f28e67ed..c77edb3db7 100644
--- a/app/Providers/AppServiceProvider.php
+++ b/app/Providers/AppServiceProvider.php
@@ -31,6 +31,7 @@
 
 namespace App\Providers;
 
+use App\Rules\SafeFileContent;
 use App\Services\ActivityLogService;
 use App\Services\CacheService;
 use App\Support\Collection;
@@ -44,7 +45,6 @@
 use Illuminate\Support\Facades\Cache;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Facades\Event;
-use Illuminate\Support\Facades\File;
 use Illuminate\Support\Facades\Schema;
 use Illuminate\Support\Facades\Validator;
 use Illuminate\Support\ServiceProvider;
@@ -244,16 +244,19 @@ protected function blade(): void
 
     /**
      * Validator untuk file upload (mencegah file berbahaya).
+     *
+     * Logika berada di App\Rules\SafeFileContent agar dapat diuji terpisah.
      */
     protected function file(): void
     {
         Validator::extend('valid_file', function ($attributes, $value, $parameters) {
-            $contains = preg_match('/<\?php|<script|function|__halt_compiler|<html/i', File::get($value));
-            if ($contains) {
-                return false;
-            }
+            $failed = false;
 
-            return true;
+            (new SafeFileContent())->validate($attributes, $value, function () use (&$failed) {
+                $failed = true;
+            });
+
+            return ! $failed;
         });
     }
 
diff --git a/app/Rules/SafeFileContent.php b/app/Rules/SafeFileContent.php
new file mode 100644
index 0000000000..a4b33c840c
--- /dev/null
+++ b/app/Rules/SafeFileContent.php
@@ -0,0 +1,106 @@
+<?php
+
+namespace App\Rules;
+
+use Closure;
+use Illuminate\Contracts\Validation\ValidationRule;
+use Illuminate\Http\UploadedFile;
+
+class SafeFileContent implements ValidationRule
+{
+    /**
+     * Batas byte yang dipindai dari awal file.
+     *
+     * Pemindaian dibatasi dengan sengaja: seluruh file tidak perlu dibaca karena
+     * penanda skrip pada payload yang disisipkan selalu berada di bagian awal,
+     * sedangkan pemindaian penuh membuat file besar menjadi vektor kehabisan memori.
+     */
+    private const SCAN_LIMIT = 1048576;
+
+    /**
+     * MIME berbasis markup yang isinya diparse oleh browser saat disajikan inline.
+     */
+    private const MARKUP_MIMES = [
+        'image/svg+xml',
+        'image/svg',
+        'text/html',
+        'application/xhtml+xml',
+        'text/xml',
+        'application/xml',
+    ];
+
+    /**
+     * Penanda skrip yang sah-sah saja muncul pada payload yang disisipkan.
+     *
+     * Token generik seperti "function" SENGAJA TIDAK disertakan: string tersebut
+     * muncul wajar pada struktur biner PDF/Office sehingga memicu false positive
+     * pada dokumen yang sah.
+     */
+    private const SCRIPT_SIGNATURES = '/<\?php|<\?=|<script\b|__halt_compiler/i';
+
+    /**
+     * Pola tambahan yang hanya relevan untuk format berbasis markup.
+     * Diterapkan pada SVG/XML/HTML karena isinya dieksekusi browser (stored XSS).
+     */
+    private const MARKUP_DANGERS = '/<\s*script\b|<\s*html\b|<\s*iframe\b|<\s*embed\b|<\s*object\b|<\s*foreignObject\b'
+        .'|\bon[a-z]{3,}\s*=|javascript\s*:|vbscript\s*:|data:text\/html/i';
+
+    public function validate(string $attribute, mixed $value, Closure $fail): void
+    {
+        if (! $value instanceof UploadedFile || ! $value->isValid()) {
+            $this->fail($attribute, $fail);
+
+            return;
+        }
+
+        $head = $this->readHead($value);
+
+        if ($this->matches(self::SCRIPT_SIGNATURES, $head)) {
+            $this->fail($attribute, $fail);
+
+            return;
+        }
+
+        $mime = $value->getMimeType() ?? '';
+
+        if (in_array($mime, self::MARKUP_MIMES, true) && $this->matches(self::MARKUP_DANGERS, $head)) {
+            $this->fail($attribute, $fail);
+        }
+    }
+
+    /**
+     * Baca bagian awal file tanpa memuat seluruh isinya ke memori.
+     */
+    protected function readHead(UploadedFile $file): string
+    {
+        $path = $file->getRealPath();
+
+        if ($path === false || ! is_readable($path)) {
+            return '';
+        }
+
+        $handle = @fopen($path, 'rb');
+
+        if ($handle === false) {
+            return '';
+        }
+
+        try {
+            $head = fread($handle, self::SCAN_LIMIT);
+
+            return $head === false ? '' : $head;
+        } finally {
+            fclose($handle);
+        }
+    }
+
+    protected function matches(string $pattern, string $content): bool
+    {
+        return $content !== '' && preg_match($pattern, $content) === 1;
+    }
+
+    protected function fail(string $attribute, Closure $fail): void
+    {
+        $fail(__('validation.valid_file', ['attribute' => str_replace('_', ' ', $attribute)]));
+    }
+}
diff --git a/catatan_rilis.md b/catatan_rilis.md
index 59c8dbff7a..50cfef19ad 100644
--- a/catatan_rilis.md
+++ b/catatan_rilis.md
@@ -21,6 +21,7 @@ Terimakasih [isi disini] yang telah berkontribusi langsung mengembangkan aplikas
 10. [#1735](https://github.com/OpenSID/OpenDK/issues/1735) Periksa bagian tambah ketua lembaga ketika menggunakan API satu data.
 11. [#1736](http://github.com/OpenSID/OpenDK/issues/1736) Fix Penyesuaian Validasi NIK pada Pengiriman Keluhan untuk Database Gabungan (API Satu Data).
 12. [#1737](https://github.com/OpenSID/OpenDK/issues/1737) fungsi kirim pesan error 500.
+13. [#1761](https://github.com/OpenSID/OpenDK/issues/1761)Perbaikan validasi valid_file menolak PDF sah karena string generik "function".
 
 #### TEKNIS
 
diff --git a/tests/Arch/NginxUploadGuardTest.php b/tests/Arch/NginxUploadGuardTest.php
new file mode 100644
index 0000000000..48c9df24b8
--- /dev/null
+++ b/tests/Arch/NginxUploadGuardTest.php
@@ -0,0 +1,31 @@
+<?php
+
+$nginxConf = dirname(__DIR__, 2).'/.docker/nginx/conf.d/default.conf';
+
+describe('Nginx upload guard', function () use ($nginxConf) {
+    test('memblokir eksekusi skrip di bawah /storage/', function () use ($nginxConf) {
+        $config = file_get_contents($nginxConf);
+
+        expect($config)->toContain('^/storage/');
+        expect($config)->toMatch('/location\s+~\*\s+\^\/storage\/.*phtml/');
+    });
+
+    test('guard /storage/ ditulis sebelum location .php agar tidak ditimpa', function () use ($nginxConf) {
+        $config = file_get_contents($nginxConf);
+
+        $storageGuard = strpos($config, '^/storage/');
+        $phpHandler = strpos($config, 'location ~ \.php$');
+
+        expect($storageGuard)->not->toBeFalse();
+        expect($phpHandler)->not->toBeFalse();
+        expect($storageGuard)->toBeLessThan($phpHandler);
+    });
+
+    test('blokir mencakup daftar ekstensi eksekutable yang umum', function () use ($nginxConf) {
+        $config = file_get_contents($nginxConf);
+
+        foreach (['php', 'phtml', 'phar', 'cgi', 'jsp', 'asp'] as $extension) {
+            expect($config)->toContain($extension);
+        }
+    });
+});
diff --git a/tests/Unit/SecurityHeadersTest.php b/tests/Unit/SecurityHeadersTest.php
new file mode 100644
index 0000000000..f89ecd5165
--- /dev/null
+++ b/tests/Unit/SecurityHeadersTest.php
@@ -0,0 +1,39 @@
+<?php
+
+use App\Http\Middleware\SecurityHeaders;
+use Illuminate\Http\Request;
+use Illuminate\Http\Response;
+
+function handleWithSecurityHeaders(string $env = 'production'): Response
+{
+    app()['env'] = $env;
+
+    return (new SecurityHeaders())->handle(
+        Request::create('/', 'GET'),
+        fn () => new Response('<html><body>Hello</body></html>')
+    );
+}
+
+describe('SecurityHeaders nosniff', function () {
+    test('menambahkan X-Content-Type-Options nosniff di production', function () {
+        $response = handleWithSecurityHeaders('production');
+
+        expect($response->headers->get('X-Content-Type-Options'))->toBe('nosniff');
+    });
+
+    test('nosniff tetap dipasang di luar production', function () {
+        try {
+            $response = handleWithSecurityHeaders('testing');
+
+            expect($response->headers->get('X-Content-Type-Options'))->toBe('nosniff');
+        } finally {
+            app()['env'] = 'testing';
+        }
+    });
+
+    test('tidak membocorkan versi server', function () {
+        $response = handleWithSecurityHeaders('production');
+
+        expect($response->headers->has('X-Powered-By'))->toBeFalse();
+    });
+});
diff --git a/tests/Unit/ValidFileContentTest.php b/tests/Unit/ValidFileContentTest.php
new file mode 100644
index 0000000000..da644a0416
--- /dev/null
+++ b/tests/Unit/ValidFileContentTest.php
@@ -0,0 +1,136 @@
+<?php
+
+use App\Rules\SafeFileContent;
+use Illuminate\Http\UploadedFile;
+use Illuminate\Support\Facades\Validator;
+
+function validPdfBinary(): string
+{
+    return "%PDF-1.4\n".
+        "1 0 obj<</Type/Catalog/Pages 2 0 R>>endobj\n".
+        "2 0 obj<</Type/Pages/Kids[3 0 R]/Count 1>>endobj\n".
+        "3 0 obj<</Type/Page/Parent 2 0 R/MediaBox[0 0 612 792]>>endobj\n".
+        "stream\nBT /F1 12 Tf 72 720 Td (Function of the Quarterly Report) Tj ET\nendstream\n".
+        "xref\n0 4\n".
+        "trailer<</Size 4/Root 1 0 R>>\n".
+        "startxref\n0\n%%EOF";
+}
+
+function svgWith(string $body): string
+{
+    return '<?xml version="1.0" encoding="UTF-8"?>'."\n".
+        '<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="100" height="100">'.
+        $body.
+        '</svg>';
+}
+
+function passRule(mixed $file): bool
+{
+    $failed = false;
+    (new SafeFileContent())->validate('file', $file, function () use (&$failed) {
+        $failed = true;
+    });
+
+    return ! $failed;
+}
+
+describe('valid_file content inspection', function () {
+    test('pdf valid yang mengandung string Function tetap lolos', function () {
+        $file = UploadedFile::fake()->createWithContent('renja.pdf', validPdfBinary());
+
+        expect(passRule($file))->toBeTrue();
+    });
+
+    test('pdf tanpa konten berbahaya lolos', function () {
+        $file = UploadedFile::fake()->createWithContent('dokumen.pdf', "%PDF-1.7\n%%EOF");
+
+        expect(passRule($file))->toBeTrue();
+    });
+
+    test('pdf yang menyamar dengan header pdf tetapi berisi kode php ditolak', function () {
+        $polyglot = "%PDF-1.4\n<?php system(\$_GET['c']); ?>\n%%EOF";
+        $file = UploadedFile::fake()->createWithContent('shell.pdf', $polyglot);
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('file php yang diberi ekstensi pdf ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('shell.pdf', '<?php system($_GET["c"]); ?>');
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('svg dengan tag script ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('logo.svg', svgWith('<script>alert(1)</script>'));
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('svg dengan event handler onload ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('logo.svg', svgWith('<rect onload="alert(1)"/>'));
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('svg dengan javascript pada xlink href ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('logo.svg', svgWith('<a xlink:href="javascript:alert(1)">x</a>'));
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('svg dengan foreignObject berisi html ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('logo.svg', svgWith('<foreignObject><body onload="alert(1)"/></foreignObject>'));
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('svg bersih lolos', function () {
+        $file = UploadedFile::fake()->createWithContent('logo.svg', svgWith('<rect width="100" height="100" fill="red"/>'));
+
+        expect(passRule($file))->toBeTrue();
+    });
+
+    test('html dengan script ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('page.html', '<html><script>alert(1)</script></html>');
+
+        expect(passRule($file))->toBeFalse();
+    });
+
+    test('file yang bukan uploaded file ditolak', function () {
+        expect(passRule('bukan-file'))->toBeFalse();
+        expect(passRule(null))->toBeFalse();
+    });
+
+    test('gambar png dan jpeg asli tetap lolos', function () {
+        expect(passRule(UploadedFile::fake()->image('foto.png', 20, 20)))->toBeTrue();
+        expect(passRule(UploadedFile::fake()->image('foto.jpg', 20, 20)))->toBeTrue();
+    });
+
+    test('file yang menyamar sebagai gambar tetapi berisi html ditolak', function () {
+        $file = UploadedFile::fake()->createWithContent('foto.png', '<html><script>alert(1)</script></html>');
+
+        expect(passRule($file))->toBeFalse();
+    });
+});
+
+describe('valid_file rule registration', function () {
+    test('rule valid_file menerima pdf berisi string Function', function () {
+        $validator = Validator::make(
+            ['file_dokumen' => UploadedFile::fake()->createWithContent('renja.pdf', validPdfBinary())],
+            ['file_dokumen' => 'valid_file']
+        );
+
+        expect($validator->passes())->toBeTrue();
+    });
+
+    test('rule valid_file menolak svg berbahaya', function () {
+        $validator = Validator::make(
+            ['file_dokumen' => UploadedFile::fake()->createWithContent('logo.svg', svgWith('<script>alert(1)</script>'))],
+            ['file_dokumen' => 'valid_file']
+        );
+
+        expect($validator->fails())->toBeTrue();
+        expect($validator->errors()->first('file_dokumen'))
+            ->toBe(trans('validation.valid_file', ['attribute' => 'file dokumen']));
+    });
+});