On a Firefox Mobile, every time I enter a search term in the top search box in a mobile version of a Wikimedia site (e.g. fr.wikipedia), some letters are repeated. More precisely it appears like this, if I try to enter "Abcde":
And then the letters are entered correctly. It behaves identically if I try to add letters to an existing search term.
This doesn't happen in Chrome or the default browser on the same device.
Samsung Galaxy Note 3