TYPO3 Core

We encounter troubles with today's Git-master (6.0-dev) and the Flash-Uploader feature:

File uploads without the flash uploader work as expected.

When the Flash Uploader is activated in the user's settings and I (logged in as admin user) click the upload icon in the file list, the pop-up with the Flash uploader shows up as expected.

The upload process itself is terminated with an error 500 (logged to apache's access (!) log). No entry in the error-log or the PHP log at all. The error message shown to the User is visible in the attached screenshot.

We were able to reproduce this issue both on a customer's development environment that contains some extensions AND also on a naked installation that doesn't contain anything but the Core. One installation runs on Ubuntu with Apache, PHP-FPM (no mod_security or SELinux installed) - the other installation runs on my MacBook with Apache and mod_php from MacPorts. The image we tried to upload is a PNG with only some KB size, the target directory is writable for the Apache-User.