Spoiler (noun)

Information about a plot or outcome that ruins the surprise or suspense for the audience.

Origin:

From the verb "spoil" + the suffix "-er".

Examples:

1. He didn't want to know the ending of the movie, so he avoided all spoilers.
2. She ruined the surprise by giving away the spoilers in the book.
3. I can't believe you just gave away the biggest spoiler in the movie!
4. The spoilers about the final episode have been circulating for weeks.
5. I wish people would stop posting spoilers on social media.