Description

Seems that jQuery 3 replaces%20 char sequence to+ in a request body during PUT and POST. A request like

$.ajax({method:'put',url:'/test/doc',dataType:'json',headers:{'content-type':'application/json'},data:JSON.stringify({val:'%20'})})

actually sends{"val":"+"} in 3.2.1 and 3.3.1, both with Migration tools.

jQuery however 2.x behaves correctly.

Update. Seems the reason is this blockhttps://github.com/jquery/jquery/blob/master/src/ajax.js#L617-L621. It assumess.contentType is the only source ofContent-Type header, but there can bes.headers['content-type'], which later (https://github.com/jquery/jquery/blob/master/src/ajax.js#L648-L650) overridess.contentType value.