Gnome developer Jordan Petridis submitted proposals to both GNOME and Firefox for disabling what he called the "abomination" that is middle-mouse paste.

In the Firefox proposal, titled "Get `middlemouse.paste` from system," there were comments such as, "Middlepaste is bad and needs to be disabled by default," but several commenters made it very clear that they'd like to see it remain.

There are those who claim that middle-mouse paste is a security issue, with one commenter saying, "middle-clicking could paste sensitive information (e.g., passwords from a password manager) into a page when the user does not intend to and without the user's knowledge."

The thing is, that can happen with Ctrl-V as well. Given that this feature has been around for a very long time, it's my opinion (as someone who's been using Linux since 1997) that this is short-sighted.

Middle-mouse paste was added to Wayland 10 years ago. If Firefox were to remove it, it could well be the only desktop application that doesn't support the feature.

One of the reasons why I use middle mouse paste is that it makes it possible to copy two different strings and paste one with Ctrl-v and the other with middle mouse paste.

There's no way of knowing if other desktops and apps will follow suit. For those who do depend on the feature, a different desktop might be the only solution if Gnome were to follow through with the proposal.