"Add media by URL" does not work on our Servers
we are currently working with TYPO3 8.4 and activated fluid_styled_content.
While editing/creating a content element of type "Text/Media" we have the possibility to "Add media by URL". After inserting a link to YouTube and clicking on "Add" a new media record was created, but the preview image is grey with the text: "File not found". Further the YouTube-ID is missing in the path of the iframe in FE. So video can't be started.
The problem seems to be in the path generation. You create a temporary path with GeneralUtility::tempname which will result in "/kunden/..." on our Servers. But the content of PATH_site is "/www/...". While checking them against each other in GeneralUtility::writeFileToTypo3tempDir following line will be returned:
return '"' . $fI['dirname'] . '" was not within directory PATH_site + "typo3temp/"';
On our servers /www is a symlink to /kunden. So it would be good to read the target of symlink of PATH_site before checking them against the result of tempnam().