[BUGFIX] Strip superfluous srcset path prefix

Rendering image '<source>' elements using the
IMAGE content object (layoutKey 'picture')
no longer have the document root path prepended
in the 'srcset' attribute.

Resolves: #100867
Related: #95379
Releases: main, 12.4
Change-Id: Id49b0f9a41dd9760e25fc17386cae805f66083e9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79682


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/frontend/Classes/ContentObject/ImageContentObject.php

@@ -214,14 +214,17 @@ class ImageContentObject extends AbstractContentObject
                     $sourceConfiguration['height'] = $sourceInfo[1];
 
                     $urlPrefix = '';
+                    $publicUrl = str_starts_with($sourceInfo[3], Environment::getPublicPath())
+                        ? PathUtility::stripPathSitePrefix($sourceInfo[3])
+                        : $sourceInfo[3];
 
                     // Prepend 'absRefPrefix' to file path only if file was not processed
                     // by FAL, e.g. GIFBUILDER
-                    if (!isset($sourceInfo['originalFile']) && is_file(Environment::getPublicPath() . '/' . $sourceInfo['3'])) {
+                    if (!isset($sourceInfo['originalFile']) && is_file(Environment::getPublicPath() . '/' . $publicUrl)) {
                         $urlPrefix = $tsfe->absRefPrefix;
                     }
 
-                    $sourceConfiguration['src'] = htmlspecialchars($urlPrefix . $sourceInfo[3]);
+                    $sourceConfiguration['src'] = htmlspecialchars($urlPrefix . $publicUrl);
                     $sourceConfiguration['selfClosingTagSlash'] = $this->getPageRenderer()->getDocType()->isXmlCompliant() ? ' /' : '';
 
                     $oneSourceCollection = $this->markerTemplateService->substituteMarkerArray($sourceLayout, $sourceConfiguration, '###|###', true, true);