[Webkit-unassigned] [Bug 211778] New: Request header field Pragma is not allowed by Access-Control-Allow-Headers

Tue May 12 06:12:31 PDT 2020

https://bugs.webkit.org/show_bug.cgi?id=211778

            Bug ID: 211778
           Summary: Request header field Pragma is not allowed by
                    Access-Control-Allow-Headers
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Page Loading
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: nigel at cherrybyte.me.uk
                CC: beidson at apple.com

Using STN Release 105 (Safari 13.2, WebKit 15610.1.10) on MacOS 10.15.5 Beta (19F83c)

I noticed some loading issues using twitter & showing response threads - which this may or may not be caused by this error. However I 
thought it worth specifically reporting an issue noted when debugging. The following request appears to be issues by the browser:

Summary
URL: https://api.twitter.com/live_pipeline/events?topic=%2Ftweet_engagement%2F1259892518163972097
Status: —
Source: —

Request
Accept: text/event-stream
Cache-Control: no-cache
Origin: https://twitter.com
Referer: https://twitter.com/TheRealDoctorT/status/1259892518163972097
User-Agent: "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.1 Safari/605.1.15"
Pragma: no-cache

Response
No response headers

Query String Parameters
topic: /tweet_engagement/1259892518163972097

The response of STN - as well as safari - is 
Failed to load resource: FetchEvent.respondWith received an error: TypeError: request header field Pragma is not allowed by Access-Control-Allow-Headers

However I do NOT notice these errors in the web tools under firefox, brave, chrome.

Further if I try and compose that request in 'postman' I see the request formed as:

curl --location --request POST 'https://twitter.com/TheRealDoctorT/status/1259892518163972097' \
--header 'Accept: text/event-stream' \
--header 'Cache-Control: no-cache' \
--header 'Origin: https://twitter.com' \
--header 'Referer: https://twitter.com/TheRealDoctorT/status/1259892518163972097' \
--header 'User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.1 Safari/605.1.15' \
--header 'Pragma: no-cache' \
--header 'Content-Type: application/json' \
--header 'Cookie: _twitter_sess=BAh7CSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNo%250ASGFzaHsABjoKQHVzZWR7ADoPY3JlYXRlZF9hdGwrCAysmwhyAToMY3NyZl9p%250AZCIlNzBmOTI1YzA4OGJlNjdjMjUzNzE0MjA1Y2M5YjcxN2M6B2lkIiVjZGE3%250AZTU5ZmZkZDI1YzdmYTgxZTYwNjhhNmFlZjZhMg%253D%253D--cdb717ebccb83bd97971e4a57daa5e6ceaf1a049; personalization_id="v1_kmuY97VchVluFNvebXMT8Q=="; guest_id=v1%3A158928231937028069; ct0=763d9b79ef3cfde6fa820fe6b96c1c97' \
--data-raw ' {}'

I didn't add the cookie and not sure where it came from... it's the closest I can get to what stn is doing.

Then I get a valid response ie 

<!DOCTYPE html>
<html dir="ltr" lang="en">
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=0,viewport-fit=cover" />
<link rel="preconnect" href="//abs.twimg.com" />
<link rel="preconnect" href="//api.twitter.com" />
<link rel="preconnect" href="//pbs.twimg.com" />
<link rel="preconnect" href="//t.co" />
<link rel="preconnect" href="//video.twimg.com" />
<link rel="dns-prefetch" href="//abs.twimg.com" />
.... and this continues

Is webkit doing something odd to fail this request?

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