Canonical, the company behind Ubuntu has seemingly disabled downloads of its latest release, Ubuntu 17.10. Those attempting to grab the build will have the option of downloading the 16.04 LTS release but when scrolling to the new 17.10 release, it says that users are "discouraged" from using this version due to a bug which corrupts the BIOS on many Lenovo laptops.
To mitigate the problem, Canonical is disabling the Intel SPI driver in the Linux 4.13 kernel which it ships with Ubuntu 17.10. When the new kernel has been built and packaged with the release, the company will make new ISOs available on its website. It’s unclear how long this process will take but, hopefully, it shouldn't be very long before a patched build is made available.
Unfortunately, if you’ve corrupted the BIOS on your Lenovo laptop, you may have to replace the machine's motherboard if it doesn't host a removable flash chip. According to reports, some Yoga and IdeaPad products have been affected as well, along with a few Acer, Toshiba and Dell laptops. Once affected, it may be impossible for your computer to handle booting from USB devices but booting from a CD should still work fine. Users also reported that BIOS settings aren't being saved either.
Issues like these are extremely rare, but if you want to make sure that you don’t run into such problems, it’s best to stick to the Long Term Support releases which have gone under far more scrutinous testing by Canonical and the public.