Slander and talebearing are prohibited (haram).
Allah Most High says, “O you who believe! Avoid much suspicion, for some suspicions are a sin. Do not spy on one another, nor backbite one another. Would one of you love to eat the flesh of his dead brother? Nay, you would abhor it, [so similarly, avoid backbiting]. And fear Allah. Indeed, Allah is Most Forgiving, Most Merciful.” [Qur’an, 49:12]
And He Most High says, “Woe to whoever disparages others behind their back or to their face.” [Qur’an, 104:1]
Hudhaifa reported that the Messenger of Allah (Allah bless him and give him peace) said, “A slanderer will not enter the Garden.” [Bukhari; Muslim]
Ibn ‘Abbas reported that the Prophet (Allah bless him and give him peace) passed by two graves and said, “They are being punished and not for anything very great. One of them did not guard himself from urine and the other was involved in backbiting.” [Bukhari; Muslim]
Imam Nawawi said, “Slander and talebearing are two of the ugliest and most frequently met with qualities among men, few people being safe from them… Every legally responsible person should refrain from saying anything except when there is a clear advantage to speaking.” [Keller, Reliance of the Traveller]
The scholars say there is nothing like safety. Therefore, one should remember the words of the Messenger of Allah (Allah bless him and give him peace), “Whoever believes in Allah and the Last day, let him say the good or remain silent.” [Bukhari; Muslim]
And Allah alone gives success.