diff --git a/.env b/.env
index 248254344..a207060a6 100644
--- a/.env
+++ b/.env
@@ -60,3 +60,7 @@ MAILER_DSN=smtp://localhost
 
 # Set canonical in the general config. Keep empty to not use it.
 BOLT_CANONICAL=
+
+# Ensure you set your trusted hosts to prevent Host Header Injection
+# See https://symfony.com/doc/current/reference/configuration/framework.html#trusted-hosts
+#SYMFONY_TRUSTED_HOSTS='^example\.com$'
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 432c5fa3a..04b998e49 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,33 @@
 Changelog
 =========
 
+## 6.1.3
+
+Released: 2026-05-16
+
+This release includes security-related fixes. Our thanks to @chndlrx and @kouz75 for identifying these issues and disclosing them to us responsibly! 👏🙏
+
+### 🔐 Security related changes
+
+- Prevent user to create/delete folder/files anywhere (@kouz75, https://github.com/bolt/core/pull/3717)
+- Switch to SVG-sanitation library to sanitise uploaded SVG files (@bobvandevijver, https://github.com/bolt/core/pull/3723)
+- Enable SYMFONY_TRUSTED_HOSTS configuration by default (@bobvandevijver, https://github.com/bolt/core/pull/3723)
+
+## 6.1.2
+
+Released: 2026-04-27
+
+Bugfix release for MySQL platform.
+ - [#3710](https://github.com/bolt/core/pull/3710)
+ - [#3713](https://github.com/bolt/core/pull/3713)
+
+## 6.1.1
+
+Released: 2026-04-24
+
+Maintenance release bumping some dependencies.
+Bolt now also disables the save button during form submission.
+
 ## 6.1.0
 
 Released: 2026-04-09
diff --git a/assets/js/version.js b/assets/js/version.js
index 7d1f5d2e1..f946659d5 100644
--- a/assets/js/version.js
+++ b/assets/js/version.js
@@ -1,2 +1,2 @@
 // generated by genversion
-export const version = '6.1.2';
+export const version = '6.1.3';
diff --git a/composer.json b/composer.json
index e9fc7d417..b78149b36 100644
--- a/composer.json
+++ b/composer.json
@@ -26,6 +26,7 @@
         "doctrine/orm": "^3.5",
         "drupol/composer-packages": "^2.0",
         "embed/embed": "^4.4",
+        "enshrined/svg-sanitize": "^0.22.0",
         "erusev/parsedown": "^1.8",
         "erusev/parsedown-extra": "^0.9",
         "fakerphp/faker": "^1.16",
diff --git a/config/packages/framework.yaml b/config/packages/framework.yaml
index 00f1e2b0a..5197c7203 100644
--- a/config/packages/framework.yaml
+++ b/config/packages/framework.yaml
@@ -3,7 +3,8 @@ framework:
   secret: '%env(APP_SECRET)%'
   csrf_protection: { enabled: true }
   http_method_override: true
-  trusted_hosts: ~
+  trusted_hosts:
+    - '%env(default::SYMFONY_TRUSTED_HOSTS)%'
   
   # Enables session support. Note that the session will ONLY be started if you read or write from it.
   # Remove or comment this section to explicitly disable session support.
diff --git a/package-lock.json b/package-lock.json
index 02ea38cd6..a64c15d23 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -24785,9 +24785,9 @@
             }
         },
         "node_modules/systeminformation": {
-            "version": "5.31.1",
-            "resolved": "https://registry.npmjs.org/systeminformation/-/systeminformation-5.31.1.tgz",
-            "integrity": "sha512-6pRwxoGeV/roJYpsfcP6tN9mep6pPeCtXbUOCdVa0nme05Brwcwdge/fVNhIZn2wuUitAKZm4IYa7QjnRIa9zA==",
+            "version": "5.31.6",
+            "resolved": "https://registry.npmjs.org/systeminformation/-/systeminformation-5.31.6.tgz",
+            "integrity": "sha512-Uv2b2uGGM6ns+26czgW2cYRabYdnswM0ddSOOlryHOaelzsmDSet1iM/NT7VOYxW8x/BW+HkY+b1Ve2pLTSGSA==",
             "dev": true,
             "license": "MIT",
             "os": [
diff --git a/package.json b/package.json
index 489be291d..a3ba18e95 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "bolt",
-    "version": "6.1.2",
+    "version": "6.1.3",
     "homepage": "https://boltcms.io",
     "author": "Bob den Otter <bob@twokings.nl> (https://boltcms.io)",
     "license": "MIT",
diff --git a/phpstan-baseline.php b/phpstan-baseline.php
index 2e9d4aef6..ab0883bc4 100644
--- a/phpstan-baseline.php
+++ b/phpstan-baseline.php
@@ -1076,23 +1076,11 @@
 	'path' => __DIR__ . '/src/Controller/Backend/Async/UploadController.php',
 ];
 $ignoreErrors[] = [
-	'message' => '#^Method Bolt\\\\Controller\\\\Backend\\\\Async\\\\UploadController\\:\\:checkJavascriptInSVG\\(\\) has parameter \\$file with no value type specified in iterable type array\\.$#',
+	'message' => '#^Method Bolt\\\\Controller\\\\Backend\\\\Async\\\\UploadController\\:\\:sanitizeSvgContent\\(\\) has parameter \\$file with no value type specified in iterable type array\\.$#',
 	'identifier' => 'missingType.iterableValue',
 	'count' => 1,
 	'path' => __DIR__ . '/src/Controller/Backend/Async/UploadController.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Parameter \\#1 \\$string of function mb_strtolower expects string, string\\|false given\\.$#',
-	'identifier' => 'argument.type',
-	'count' => 1,
-	'path' => __DIR__ . '/src/Controller/Backend/Async/UploadController.php',
-];
-$ignoreErrors[] = [
-	'message' => '#^Parameter \\#2 \\$subject of function preg_match expects string, string\\|false given\\.$#',
-	'identifier' => 'argument.type',
-	'count' => 1,
-	'path' => __DIR__ . '/src/Controller/Backend/Async/UploadController.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Method Bolt\\\\Controller\\\\Backend\\\\BulkOperationsController\\:\\:findRecordsFromIds\\(\\) has parameter \\$ids with no value type specified in iterable type array\\.$#',
 	'identifier' => 'missingType.iterableValue',
diff --git a/public/theme/skeleton/partials/_image.twig b/public/theme/skeleton/partials/_image.twig
index d697419b6..18205ecfd 100644
--- a/public/theme/skeleton/partials/_image.twig
+++ b/public/theme/skeleton/partials/_image.twig
@@ -1,7 +1,7 @@
 {% if image %}
     <figure>
         <a href="{{ record|image }}">
-            <img src="{{ thumbnail(record, 1368, 1026) }}" alt="{{ (record|image).alt|default(record|title) }}">
+            <img src="{{ thumbnail(record, 1368, 1026, quality = 70, format = 'avif') }}" alt="{{ (record|image).alt|default(record|title) }}">
         </a>
         {% if image.alt|default() %}
             <figcaption>{{ image.alt }}</figcaption>
diff --git a/src/Controller/Backend/Async/UploadController.php b/src/Controller/Backend/Async/UploadController.php
index b1445d2ac..389ef159e 100644
--- a/src/Controller/Backend/Async/UploadController.php
+++ b/src/Controller/Backend/Async/UploadController.php
@@ -11,6 +11,7 @@
 use Bolt\Twig\TextExtension;
 use Cocur\Slugify\Slugify;
 use Doctrine\ORM\EntityManagerInterface;
+use enshrined\svgSanitize\Sanitizer;
 use Sirius\Upload\Handler;
 use Sirius\Upload\Result\File;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
@@ -150,8 +151,8 @@ public function handleUpload(Request $request): JsonResponse
 
         $uploadHandler->addRule(
             'callback',
-            ['callback' => $this->checkJavascriptInSVG(...)],
-            'It is not allowed to upload SVG\'s with embedded Javascript.',
+            ['callback' => $this->sanitizeSvgContent(...)],
+            'The SVG-file could not be sanitized automatically, is it a valid SVG-file?',
             'Upload file'
         );
 
@@ -210,18 +211,31 @@ private function sanitiseFilename(string $filename): string
         return $filename . '.' . $extension;
     }
 
-    public function checkJavascriptInSVG(array $file): bool
+    public function sanitizeSvgContent(array $file): bool
     {
         if (Path::getExtension($file['name']) != 'svg') {
             return true;
         }
 
-        $svgFile = file_get_contents($file['tmp_name']);
+        // Configure sanitizer
+        $sanitizer = new Sanitizer();
+        $sanitizer->minify(true);
+        $sanitizer->removeXMLTag(true);
+        $sanitizer->removeRemoteReferences(true);
 
-        if (preg_match('/(?:<[^>]+\s)(on\S+)=["\']?((?:.(?!["\']?\s+(?:\S+)=|[>"\']))+.)["\']?/i', $svgFile)) {
+        // Retrieve file contents
+        if (! $svgFile = file_get_contents($file['tmp_name'])) {
             return false;
         }
 
-        return mb_strpos((string) preg_replace('/\s+/', '', mb_strtolower($svgFile)), '<script') === false;
+        // Sanitize the SVG content
+        if (false === $sanitizedSvg = $sanitizer->sanitize($svgFile)) {
+            return false;
+        }
+
+        // Write the sanitized SVG back to the temporary file
+        file_put_contents($file['tmp_name'], $sanitizedSvg);
+
+        return true;
     }
 }
diff --git a/src/Controller/Backend/FilemanagerController.php b/src/Controller/Backend/FilemanagerController.php
index 6374aaa69..b2a5ec30c 100644
--- a/src/Controller/Backend/FilemanagerController.php
+++ b/src/Controller/Backend/FilemanagerController.php
@@ -20,6 +20,7 @@
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
 use Symfony\Component\Routing\Attribute\Route;
 use Symfony\Component\Security\Core\Exception\InvalidCsrfTokenException;
 
@@ -96,11 +97,15 @@ public function delete(Request $request): Response
         $path = $this->getFromRequest($request, 'path');
         $location = $this->getFromRequest($request, 'location');
 
+        if (! is_string($path)) {
+            throw new BadRequestHttpException('Invalid filename');
+        }
+
         $this->denyAccessUnlessGranted('managefiles:' . $location);
 
         $location = $this->fileLocations->get($location);
 
-        $folder = Path::canonicalize($location->getBasepath() . '/' . $path);
+        $folder = PathCanonicalize::canonicalize($location->getBasepath(), $path);
 
         if (! $this->filesystem->exists($folder)) {
             $this->addFlash('warning', 'filemanager.delete_folder_missing');
@@ -139,7 +144,7 @@ public function create(Request $request): Response
 
         $location = $this->fileLocations->get($location);
 
-        $folder = Path::canonicalize($location->getBasepath() . '/' . $path);
+        $folder = PathCanonicalize::canonicalize($location->getBasepath(), $path);
 
         if ($this->filesystem->exists($folder)) {
             $this->addFlash('warning', 'filemanager.create_folder_already_exists');
diff --git a/src/Controller/ImageController.php b/src/Controller/ImageController.php
index 3b3de5dca..6bd8378f0 100644
--- a/src/Controller/ImageController.php
+++ b/src/Controller/ImageController.php
@@ -20,6 +20,8 @@
 
 class ImageController
 {
+    private const SUPPORTED_FORMATS = ['jpg', 'webp', 'png', 'gif', 'avif'];
+
     private Server $server;
 
     /**
@@ -27,6 +29,7 @@ class ImageController
      *     w?: int,
      *     h?: int,
      *     fit?: string,
+     *     fm?: string,
      *     location?: string,
      *     q?: int
      * }
@@ -45,17 +48,22 @@ public function thumbnail(Request $request, string $paramString, string $filenam
             return $this->sendErrorImage();
         }
 
+        $this->parseParameters($paramString);
+
         try {
             $filename = PathCanonicalize::canonicalize($this->getPath($request), $filename, true);
         } catch (Exception) {
             return $this->sendErrorImage();
         }
 
-        $this->parseParameters($paramString);
+        $sourceFilename = $this->parseFormatFromFilename($filename);
+
+        $urlFilename = isset($this->parameters['fm']) && $this->parameters['fm'] !== '' ?  $sourceFilename . '.' . $this->parameters['fm']:$sourceFilename;
+
         $this->createServer($request);
-        $this->saveThumb($request, $filename);
+        $this->saveThumb($request, $sourceFilename, $urlFilename);
 
-        return $this->buildResponse($request, $filename);
+        return $this->buildResponse($request, $sourceFilename);
     }
 
     private function createServer(Request $request): void
@@ -82,7 +90,25 @@ private function getPath(Request $request, ?string $path = null, bool $absolute
         return $this->config->getPath($path, $absolute, $additional);
     }
 
-    private function saveThumb(Request $request, string $filename): void
+    private function parseFormatFromFilename(string $filename): string
+    {
+        $parts = explode('.', pathinfo($filename, PATHINFO_BASENAME));
+
+        if (count($parts) < 3) {
+            return $filename;
+        }
+
+        $ext = mb_strtolower(end($parts));
+
+        if ($this->isSupportedFormat($ext)) {
+            $this->parameters['fm'] = $ext;
+            return mb_substr($filename, 0, -(mb_strlen($ext) + 1));
+        }
+
+        return $filename;
+    }
+
+    private function saveThumb(Request $request, string $filename, string $urlFilename = ''): void
     {
         if (! $this->config->get('general/thumbnails/save_files', true)) {
             return;
@@ -95,7 +121,7 @@ private function saveThumb(Request $request, string $filename): void
         $thumbPath = Path::join(
             $this->getPath($request, 'thumbs'),
             $this->parameterPath(),
-            $filename
+            $urlFilename ?: $filename
         );
 
         try {
@@ -162,21 +188,38 @@ private function parseParameters(string $paramString): void
         $this->parameters = [
             'w' => (isset($raw[0]) && is_numeric($raw[0])) ? (int) $raw[0] : 400,
             'h' => (isset($raw[1]) && is_numeric($raw[1])) ? (int) $raw[1] : 300,
-            'fit' => $raw[2] ?? $this->config->get('general/thumbnails/default_cropping', 'default'),
+            'fm' => '',
+            'fit' => $this->config->get('general/thumbnails/default_cropping', 'default'),
             'location' => 'files',
-            'q' => (! empty($raw[2]) && 0 <= $raw[2] && $raw[2] <= 100) ? (int) $raw[2] : 80,
+            'q' => $this->config->get('general/thumbnails/quality', 80)
         ];
 
-        if (isset($raw[4])) {
-            $this->parameters['fit'] = $this->parseFit($raw[3]);
-            $this->parameters['location'] = $raw[4];
-        } elseif (isset($raw[3])) {
-            $possibleFit = $this->parseFit($raw[3]);
+        $remaining = array_values(array_filter(
+            array_slice($raw, 2),
+            static fn (int|string $value): bool => $value !== ''
+        ));
+
+        if (isset($remaining[0]) && is_numeric($remaining[0]) && 0 <= (int) $remaining[0] && (int) $remaining[0] <= 100) {
+            $this->parameters['q'] = (int) array_shift($remaining);
+        }
+
+        foreach ($remaining as $token) {
+            $token = (string) $token;
+            $normalizedToken = mb_strtolower($token);
 
-            if ($this->testFit($possibleFit)) {
-                $this->parameters['fit'] = $possibleFit;
-            } else {
-                $this->parameters['location'] = $raw[3];
+            if ($this->parameters['fm'] === '' && $this->isSupportedFormat($normalizedToken)) {
+                $this->parameters['fm'] = $normalizedToken;
+                continue;
+            }
+
+            $fit = $this->parseFit($normalizedToken);
+            if ($this->testFit($fit)) {
+                $this->parameters['fit'] = $fit;
+                continue;
+            }
+
+            if ($this->parameters['location'] === 'files') {
+                $this->parameters['location'] = $token;
             }
         }
     }
@@ -203,6 +246,11 @@ private function testFit(string $fit): bool
         return (bool) preg_match('/^(contain|max|fill|stretch|crop)(-.+)?/', $fit);
     }
 
+    private function isSupportedFormat(string $format): bool
+    {
+        return in_array($format, self::SUPPORTED_FORMATS, true);
+    }
+
     public function parseFit(string $fit): string
     {
         return match ($fit) {
@@ -217,14 +265,15 @@ public function parseFit(string $fit): string
 
     private function parameterPath(): string
     {
-        return sprintf(
-            '%d_%d_%d_%s_%s',
+        $parts = array_filter([
             $this->parameters['w'] ?? 0,
             $this->parameters['h'] ?? 0,
-            $this->parameters['q'] ?? 0,
-            $this->parameters['fit'] ?? '',
-            $this->parameters['location'] ?? ''
-        );
+            $this->parameters['q'] ?? 80,
+            $this->parameters['fit'] ?? null,
+            $this->parameters['location'] ?? 'files',
+        ], fn (int|string|null $v): bool => $v !== null && $v !== '' && $v !== 0);
+
+        return implode('×', $parts);
     }
 
     public function sendErrorImage(): Response
diff --git a/src/Twig/ImageExtension.php b/src/Twig/ImageExtension.php
index c41e42ac2..889c71e5d 100644
--- a/src/Twig/ImageExtension.php
+++ b/src/Twig/ImageExtension.php
@@ -102,11 +102,11 @@ public function showImage($image, ?int $width = null, ?int $height = null, ?bool
     /**
      * @param ImageField|array|string $image
      */
-    public function thumbnail($image, ?int $width = null, ?int $height = null, ?string $location = null, ?string $path = null, ?string $fit = null, ?int $quality = null): string
+    public function thumbnail($image, ?int $width = null, ?int $height = null, ?string $location = null, ?string $path = null, ?string $fit = null, ?int $quality = null, ?string $format = null): string
     {
         $filename = $this->getFilename($image, true);
 
-        return $this->thumbnailHelper->path($filename, $width, $height, $location, $path, $fit, $quality);
+        return $this->thumbnailHelper->path($filename, $width, $height, $location, $path, $fit, $quality, $format);
     }
 
     /**
diff --git a/src/Utils/ThumbnailHelper.php b/src/Utils/ThumbnailHelper.php
index ae668d0ce..f222b30b6 100644
--- a/src/Utils/ThumbnailHelper.php
+++ b/src/Utils/ThumbnailHelper.php
@@ -27,18 +27,22 @@ private function parameters(?int $width = null, ?int $height = null, ?string $fi
             $height = 10000;
         }
 
-        if ($location === 'files') {
-            $location = null;
+        if ($location === null) {
+            $location = 'files';
         }
 
         if (! $quality && $this->config instanceof Config) {
             $quality = (int) $this->config->get('general/thumbnails/quality');
         }
 
+        if ($fit === null && $this->config instanceof Config) {
+            $fit = $this->config->get('general/thumbnails/default_cropping', 'default');
+        }
+
         return implode('×', array_filter([$width, $height, $quality, $fit, $location]));
     }
 
-    public function path(?string $filename = null, ?int $width = null, ?int $height = null, ?string $location = null, ?string $path = null, ?string $fit = null, ?int $quality = null): string
+    public function path(?string $filename = null, ?int $width = null, ?int $height = null, ?string $location = null, ?string $path = null, ?string $fit = null, ?int $quality = null, ?string $format = null): string
     {
         if (! $filename) {
             return '/assets/images/placeholder.png';
@@ -47,7 +51,9 @@ public function path(?string $filename = null, ?int $width = null, ?int $height
         if ($path) {
             $filename = $path . '/' . $filename;
         }
-
+        if ($format) {
+            $filename .= '.' . $format;
+        }
         $paramString = $this->parameters($width, $height, $fit, $location, $quality);
         $filename = Str::ensureStartsWith($filename, '/');
 
diff --git a/src/Version.php b/src/Version.php
index 473e9f7a0..effa27299 100644
--- a/src/Version.php
+++ b/src/Version.php
@@ -23,7 +23,7 @@ final class Version
      *   Stable — 3.0.0
      *   Development — 3.1.0 alpha 1
      */
-    public const VERSION = '6.1.2';
+    public const VERSION = '6.1.3';
 
     public const CODENAME = '';
 
diff --git a/yaml-migrations/m_2026-05-14-framework.yaml b/yaml-migrations/m_2026-05-14-framework.yaml
new file mode 100644
index 000000000..6e6e15b58
--- /dev/null
+++ b/yaml-migrations/m_2026-05-14-framework.yaml
@@ -0,0 +1,7 @@
+file: packages/framework.yaml
+since: 6.1.3
+
+add:
+  framework:
+    trusted_hosts:
+      - '%env(default::SYMFONY_TRUSTED_HOSTS)%'