On March 9, Rumeysa Ozturk, a Turkish graduate student at Tufts University, sent an anxious text message to Najiba Akbar, the university’s former Muslim chaplain, with whom she had become close.

“I recently learned that someone added all my information to a doxxing website called Canary Mission because of the op-ed published last March,” Ms. Ozturk wrote. She was trying to figure out what to do about it.

The website published her résumé and a picture of her in a red head scarf, and…