Used libmagic versions are not documented

Description

Prior to PHP 8, the finfo extension would always report that files with the .txt extension had a mime type of text/plain (I think). Certainly, files that had contents that looked like CSV would return a mime type of text/plain.

From PHP 8.0.1 to 8.0.25, the finfo extension returns a mime type of application/csv if the file contains something that looks like CSV.

From PHP 8.1.0+, the finfo extension returns a mime type of text/csv if the file contains something that looks like CSV.

This is demonstrated at https://3v4l.org/tmGQe

I'm not sure if this change of behaviour is deliberate or unintentional.

• If deliberate, then it is a breaking change that ought to be documented, but I cannot find any mention of it in any of the release notes or the php documentation for finfo. (So, in that case, I have misfiled this report. It ought to be a documentation bug.)
• If unintentional, then I note that there are potential security implications if a file that advertises itself via its extension as a plain text file is treated as something different because finfo has looked inside it and decided it is something else. Therefore, someone should review whether the previous behaviour ought to be reverted.

PHP Version

PHP 7.x - 8.x

Operating System

Ubuntu 20.04 - 22.04

Start with the finfo documentation and PHP release notes covering PHP 8.0.1 through 8.1.0, then compare the CSV MIME-type behavior in the linked 3v4l reproduction. Determine whether the change was deliberate and document it, or establish that the behavior belongs in a separate bug investigation.