Vanessa Williams -- I Was Molested as a Child

Vanessa Williams says she was sexually abused as a 10-year-old girl ... and believes the traumatizing experience caused her to become "highly sexualized" at an abnormally young age.

Williams dropped the bombshell in her new book, "You Have No Idea" ... explaining how an 18-year-old woman molested her during a family trip with friends.

The "Desperate Housewives" actress opened up about the experience to "Nightline" ... saying, "It happened one night where she told me, 'come over here,' I didn't know that it was wrong, but I knew that it wasn't right because I wasn't supposed to tell anybody."

"I think I was highly sexualized because I was in fifth grade and I had this experience. Because it feels good, you're like, OK, well this is supposed to be normal. That's not normal for a 10-year-old to be seduced."

In her book, Williams also reveals she had an abortion during her high school years ... but kept it a secret from everyone, including her mother, because she was scared.

Williams went on to become the first black Miss America in 1984 ... but was shamed into giving up her crown after several nude pictures appeared in Penthouse. Williams says she stupidly trusted the photographer when he promised to keep them private.