A crazy way broken custom JS can cause “Submission failed,” with “checksum invalid” in the details
As you read on, you might think I’ve contrived a situation with an infinitesimal chance of happening in real life, just for the love of blogging. But this just happened to a user who posted on the Nation!
So here’s the weirdest Marketo Forms factoid you may ever learn: if the 20th field added to a form has an empty name, you’ll get this generic error on submit:
And inspecting the HTTP 400 response shows:
{
"message" : "checksum invalid",
"error" : true,
"errorCode" : "400"
}
Hold on, a form field can have an empty name???
Well, no. An <input name> and <input name=""> are both prohibited by the HTML standard. A native HTML <form> submit will not send values for those inputs.
But while Marketo forms use standard HTML <input> elements — a very good thing, I always take care to say! — the data that goes on the wire is assembled using JS. (Most modern forms do this.)
The Forms 2.0 API lets you add a hidden field with an emp
