HTTP header ‘sec-ch-ua’ without value causes some iframe to not load

When I invoke AJAX request in a iframe by XMLHttpRequest, the request headers has a ‘sec-ch-ua’ header without value.

electron issue:
[Bug]: Possibly broken user agent client hint · Issue #30201 · electron/electron (

Ok, what problem does this create?

What are you trying to do that doesn’t work?

Header without value is an invalid header, the server rejected my request.

Which server?

The calibre Content server — calibre 5.41.0 documentation (

we will add the mitigation in 0.14.8

1 Like

I am still getting the error this is supposed to fix, in Version 0.15.6 (installer 0.14.15)

I don’t know what problem you have but is not this one.