KDE is an international technology team creating user-friendly free and open source software for desktop and portable computing. KDE’s software runs on GNU/Linux, BSD and other operating systems, including Windows.
If you encounter a bug, proceed to https://bugs.kde.org, check whether it has been reported.
If it hasn't, report it yourself.
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Developers do not look for reports on social media, so they will not see it and all it does is clutter up the feed.
Since the update, if I snap Firefox to the top the mouse seems to be offset a number of pixels compared to where the actual cursor is. It also affects the content in sites, not just stuff in Firefox.
Edit: Looks like it's not just when it's snapped, but as soon as it passes about the top 90% of the screen. Just took a screenshot, where you can see the cursor is hovering over Other Bookmarks, but it's activating the menu above it.
If you right-click on the Firefox toolbar, select "Customize Toolbar..." and then in the bottom left corner tick the "Title Bar" checkbox, does that change anything about it?