Fix Editor Add Problem by URL

[bqi343]

see #5682 (comment)

relevant PR: #4251

[cjspd-oly]

FAILED FOR USACO AND CODEFORCES

SyntaxError: Unexpected token 'A', "A server e"... is not valid JSON

WORKS ONLY FOR CSES AND ATCODER

[Sosuke23]

The current parser is correct, no doubt. see the example

[cjspd-oly]

@Sosuke23

[cjspd-oly]

[Sosuke23]

i am saying that the issue maybe something else

[cjspd-oly]

i am saying that the issue maybe something else

Thank you so much.

[Sosuke23]

plus it is giving 500 internal server error when you debug in network section,

[emhgit]

i investigated the issue, here are the results:

1. using codeforces URLs causes errors because invalid JSON data is return. for example, the url https://codeforces.com/problemset/problem/1660/B this error:

SyntaxError: Unexpected token 'E', "Error when"... is not valid JSON

2. i checked the backend error logs from my terminal to get more info:
   error message shown in terminal:

https://codeforces.com/problemset/problem/1660/B url

 ERROR 

Request failed with status code 403



  Error: Request failed with status code 403

  - createError.js?:16 createError
    [.]/[axios]/lib/core/createError.js?:16:15

  - settle.js?:17 settle
    [.]/[axios]/lib/core/settle.js?:17:12

  - http.js?:269 IncomingMessage.handleStreamEnd
    [.]/[axios]/lib/adapters/http.js?:269:11

  - node:events:530 IncomingMessage.emit
    node:events:530:35

  - readable:1698 endReadableNT
    node:internal/streams/readable:1698:12

  - task_queues:90 processTicksAndRejections
    node:internal/process/task_queues:90:21


Executed function "/api/fetch-metadata" in 330ms

the stack trace leads towards the axios library, so the issue is not coming from our parser. however, i am not implying that the error is axios. the 403 forbidden error code is significant.

3. i logged the request and response bodies to get more info of this error, and i found that CF provides a cloudflare challenege page in the response headers:

response: {
    status: 403,
    statusText: 'Forbidden',
    headers: {
      date: 'Sun, 12 Oct 2025 19:04:20 GMT',
      'content-type': 'text/html; charset=UTF-8',
      'content-length': '7021',
      connection: 'close',
      'accept-ch': 'Sec-CH-UA-Bitness, Sec-CH-UA-Arch, Sec-CH-UA-Full-Version, Sec-CH-UA-Mobile,
Sec-CH-UA-Model, Sec-CH-UA-Platform-Version, Sec-CH-UA-Full-Version-List, Sec-CH-UA-Platform, Sec-CH-UA,       
UA-Bitness, UA-Arch, UA-Full-Version, UA-Mobile, UA-Model, UA-Platform-Version, UA-Platform, UA',
      'cf-mitigated': 'challenge',
      // rest of response...
}

when axios gets this 403 response, it returns an error. this error is then returned, instead of the valid JSON, which causes the error to appear on the frontend UI.

i am still debugging, so i will try to research a solution to this.

[cjspd-oly]

I have tested changes. It works as expected. For CF & CSES & AtCoder.

USACO.org doesn't work.

[bqi343]

It still doesn't work for USACO though?

[cjspd-oly]

TypeError: Cannot read properties of undefined (reading 'uniqueId')

link: https://usaco.org/index.php?page=viewproblem2&cpid=993

[Sosuke23]

It seems spaces are the issue. I am verifying it. Might make a pr soon.

> <div style="position:relative; float:left; left:10px; top:-50px; width:550px;"> 
> <div class="panel">
> 
> <h2> USACO 2016 January Contest, Platinum </h2>
> <h2> Problem 1. Fort Moo </h2>
>  
> </div>
> </div>

there is nothing wrong with these.... the issue is related to some Cloudflare thing or some anti-bot measure. And it only throws an error in vercel deployment, in local it is working fine.