Steps to reproduce:
- Go to a template page (e.g. https://www.mediawiki.org/w/index.php?title=Template:Extension&action=edit) and click edit
- Click the templatedata button
- Click on a parameter
- Type something in label and/or description
Expected:
The typed text should appear in the text field
Observed:
The input will be cleared immediatly, so it's impossible to insert text there.
It's working on wikipedia's, so it's seems to be a problem in 1.25wmf21