Steps to replicate the issue (include links if applicable):

A. from T338462 experience

• Trying to edit https://commons.wikimedia.org/wiki/File:TDKGM_02.368_Mesin_Ketik_Ki_Hajar_Dewantara.webm
• After finished editing, the new description offered to me was: |description=VicuñaUploader 1.3.3a
• (That was the description from the original uploader:)

10 Januari 2023 12.55‎ Muhamad Abdu bicara kontrib‎ 284 bita +284‎ VicuñaUploader 1.3.3a

B. from T338465 experience

• Trying to edit https://commons.wikimedia.org/wiki/File:Unknown_flower_in_Tawangmangu.webm
• After finished editing, the new description offered to me was: |description=Imported media from uploads:619aa2e4-0541-11ee-a15d-92f549fe63c7 as seen here: https://commons.wikimedia.org/wiki/File:Unknown_flower_in_Tawangmangu_edited_0.webm
• (That was the description when I uploaded it with video2commons:)

7 Juni 2023 22.17‎ Bennylin bicara kontrib‎ 270 bita +270‎ Imported media from uploads:619aa2e4-0541-11ee-a15d-92f549fe63c7 Tag: video2commons [1.0]

What happens?:

Somehow it extracted the data from the first upload, which in these two cases (and I believe in most cases) doesn't make sense and doesn't fit into the description parameter (imagine if the description contain another two curly brackets)

Of course we can edit it, but it shouldn't be there in the first place. There are many ways to pre-fill the description. I kinda expected it will prefill with everything from the original file, like CropTool do.

What should have happened instead?:

the description from the original file was brought over, the description should match the original description. If it's hard to parse the data, just copy the whole content of the file page, like what CropTool do.

If it's uploaded as a new file, then you may add
|source={{Derived from|1=blablabla}}
and
{{Extracted from|File:blablabla}}

if it's not (it's being overwritten instead), then don't offer those two templates.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):