The currency symbol handling of the custom amount fields in banners on enwiki is buggy.
Steps to reproduce
- Call a banner on enwiki (e. g. https://en.wikipedia.org/?banner=B19_WMDE_EN_Desktop_02_ctrl)
- Enter a value into the custom amount field.
- Click anywhere to make the field lose the input focus.
- Click the field again and change its value without removing the currency symbol that was automatically added.
- There is only one currency character in the field.
- Although there already is one, another Euro character is added to the field.