Steps to reproduce the issue

Using frontend editing. Try to edit an existing article or create a new one and add for example a picture with umlauts in its file name. This only appears to affect frontend editing, the same works fine when editing the article in the backend as administrator.

1. Add a picture
   
2. Pick a picture with umlauts
   
3. Try to save the article
4. Experience the following error:

It's reproducible when creating a new article just consisting of the following code:

<p><img src="dateien/103/images/jubiläum_november_2015.jpg" alt="jubilaeum november 2015" style="margin: 5px 20px;"></p>

When first renaming the file replacing umlauts the same works fine.

Expected result

No error - work like before in Joomla 3.x

Actual result

Experience a timout/fatal error

System information (as much as possible)

From Joomla system information:

• Database: 10.5.18-MariaDB
• Database charset: utf8_general_ci
• Database connection charset: utf8mb4_general_ci
• PHP: 8.0.26 (but also reproducible on 7.4.33)
• Default Cassiopeia template
• JCE Editor

Additional comments

This wasn't an issue and worked fine before in Joomla 3.x before upgrading to Joomla 4.x. Raising the PHP execution timeout also doesn't help as the PHP-FPM process is taking 100% CPU no matter how long it runs until running into the timeout/error.