[soop] ERROR: unsafe file extension: 'php' when downloading thumbnail
### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm reporting that yt-dlp is broken on a **supported** site
- [X] I've verified that I have **updated yt-dlp to nightly or master** ([update instructions](https://github.com/yt-dlp/yt-dlp#update-channels))
- [X] I've checked that all provided URLs are playable in a browser with the same IP and same login details
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/yt-dlp/yt-dlp/wiki/FAQ#video-url-contains-an-ampersand--and-im-getting-some-strange-output-1-2839-or-v-is-not-recognized-as-an-internal-or-external-command)
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)
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### Region

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### Provide a description that is worded well enough to be understood

The thumbnail file is actually jpeg, but yt-dlp tries to download it as php. So it leads ERROR: unsafe file extension: 'php'

`yt-dlp --skip-download --write-thumbnail -vU https://vod.sooplive.co.kr/player/136504897`

### Provide verbose output that clearly demonstrates the problem

- [X] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [X] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
[debug] Command-line config: ['--skip-download', '--write-thumbnail', '-vU', 'https://vod.sooplive.co.kr/player/136504897']
[debug] Encodings: locale cp949, fs utf-8, pref cp949, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version master@2024.11.12.233022 from yt-dlp/yt-dlp-master-builds [f2a4983df] (win_exe)
[debug] Python 3.10.11 (CPython AMD64 64bit) - Windows-10-10.0.26100-SP0 (OpenSSL 1.1.1t  7 Feb 2023)
[debug] exe versions: ffmpeg 7.1-full_build-www.gyan.dev (setts), ffprobe 7.1-full_build-www.gyan.dev
[debug] Optional libraries: Cryptodome-3.21.0, brotli-1.1.0, certifi-2024.08.30, curl_cffi-0.5.10, mutagen-1.47.0, requests-2.32.3, sqlite3-3.40.1, urllib3-2.2.3, websockets-13.1
[debug] Proxy map: {}
[debug] Request Handlers: urllib, requests, websockets, curl_cffi
[debug] Loaded 1838 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp-master-builds/releases/latest
Latest version: master@2024.11.12.233022 from yt-dlp/yt-dlp-master-builds
yt-dlp is up to date (master@2024.11.12.233022 from yt-dlp/yt-dlp-master-builds)
[soop] Extracting URL: https://vod.sooplive.co.kr/player/136504897
[soop] 136504897: Downloading API JSON
[soop] 136504897: Downloading part 1 m3u8 information
[soop] 136504897: Downloading part 2 m3u8 information
[download] Downloading multi_video: [동출 99일차/유입 환영!]추석특집 신창섭 월드컵 엄선작
ERROR: unsafe file extension: 'php'
Traceback (most recent call last):
  File "yt_dlp\YoutubeDL.py", line 1625, in wrapper
  File "yt_dlp\YoutubeDL.py", line 1781, in __extract_info
  File "yt_dlp\YoutubeDL.py", line 1910, in process_ie_result
  File "yt_dlp\YoutubeDL.py", line 2010, in __process_playlist
  File "yt_dlp\YoutubeDL.py", line 4386, in _write_thumbnails
  File "yt_dlp\utils\_utils.py", line 2149, in _change_extension
  File "yt_dlp\utils\_utils.py", line 5232, in sanitize_extension
yt_dlp.utils._UnsafeExtensionError: unsafe file extension: 'php'
```