People do that all the time, but the results can be a mess within a rather short time. That's because the paint is wet and can loosen the wallpaper. Sometimes it happens right away, sometimes it takes some time. You're really better off removing the wallpaper and washing off the sizing and glue then start painting fresh. It will look better for longer and you won't end up with a mess that's harder to remove. Wishing you the best.
Hi Vivian! I wouldn't paint over it. I have had to remove painted wallpaper, and it was messy, difficult and something I never want to do again. Some of it peeled off on its own, and some of it had to be steamed, scraped, chemically treated and even cleaned off with a razor blade. You will create a problem for yourself in the future or for someone else. Honestly, I would never buy a house where someone had painted over the wallpaper, again. The seams show and it is a nightmare to redo.
Don't do it, you will regret it later. At one house, the man hours alone to get painted over wallpaper off would have been horrendous. I just cut the walls out and replaced. Quicker and cheaper. Do yourself a favor, remove the wallpaper, repair, dry then prime and paint.
Always best to remove the wallpaper. It can bubble or separate from moisture in the paint. Seams can show. Only time I advise painting wallpaper is if it was installed without primer or sizing. Wash it down, prime with Kilz primer, then paint your color.
Use DRYLOCK first. Then paint!