Please make an effort toward the use of unambiguous dates in your future posts. In the USA, the month is placed before the day, but in the rest of the world, the day is placed before the month. This is why the unambiguous format “YYYY.MM.DD” is preferred — you can use either periods, dashes or slashes as the separator, of course. 
That kernel version is definitely not new. It was introduced in the 2024.03.13 Stable Update. 
Yes, it’s part of the mhwd utility.
Try booting up in verbose mode to see what’s going on. At the GRUB menu — if you don’t see the menu, press Esc during the hardware boot process — select the entry for your default kernel and press E. Remove the words “quiet” and “splash” from the boot options. Then press F10 to boot the system.
I’m on Manjaro Stable with Plasma, and the only updates there have been in recent days were to the xz package, manjaro-release, and since last night, chromium. There have not been any updates to the kernel or mhwd since the 2024.03.13 Stable Update. 