Nice one as it will catch on every request the error messages.

Thank you for providing a better solution!

even better would be to display the error message from the svgsanitizer which explains exactly why the file was rejected

I have added documentation about uploading SVG files. You can find it at https://docs.joomla.org/J4.x:Media:_Uploading_SVG_files. It may need refining and additional content. You are welcome to pitch in, thank you!

IT does what it says but I wonder why we have the two messages. The second one makes the first one redundant?

The script render all messages that was sent from PHP backend.
In your example, I guess the first one comes from a controller, and second one from a validator.

I have tested this item ✅ successfully on b5feda2

Before the fix, the script was rendered only first message, and rest were ignored.

In your example, I guess the first one comes from a controller, and second one from a validator

The first message is from the Exception https://github.com/joomla/joomla-cms/blob/4.2-dev/plugins/filesystem/local/src/Adapter/LocalAdapter.php#L772 , additional messages are Joomla system messages generated by calling $app->enqueueMessage from canUpload from MediaHelper https://github.com/joomla/joomla-cms/blob/4.2-dev/libraries/src/Helper/MediaHelper.php#L200

Still the first error message is redundant as Brian said. Is it OK to make the Exception https://github.com/joomla/joomla-cms/blob/4.2-dev/plugins/filesystem/local/src/Adapter/LocalAdapter.php#L772 with empty message, and have the Joomla system messages rendered for this case ? It is kind of workaround but more user friendly.

Is it OK to make the Exception with empty message

I do not think.
I think the root issue that $helper->canUpload() should return boolean and cannot throw an exception, so someone decided to put all in to $app->enqueueMessage . Not perfect, but working.

I have tested this item ✅ successfully on b5feda2

Not perfect but work.

RTC

For Header logo fixer:
How to get Joomla4 with Cassiopeia Template to work

J4 dashboard > Content > Media > Create a new Folder "svgs"
ftp upload your svg logo file to this folder
/var/www/html/images/svgs/upload the logo

Topright "Options" in the Media
Allowed Extensions > add > "svg,SVG"
Legal Image Extensions (File Types) > add > "svg"
Legal MIME Types > add > ",image/svg+xml,application/svg+xml"

SAVE

J4 dashboard > System > Templates > Site Template Styles > Cassiopeia - Default >

/images/svgs/header-logo.svg

Tagline (this is a must-step):
i have added 20x The &nbsp entity " "

SAVE

I will update once i have a fixer for the Footer svg file ;-)

@AmyKrizanWang please do not update your comment. It is nothing to do with this issue.

This pull request has been automatically rebased to 4.3-dev.

Pleas test it again, there was a complex conflict, I had to redo changes.

This pull request has been automatically rebased to 4.4-dev.