In Talkyard, versions v0.04.01 through v0.6.74-WIP-63220cb, v0.2020.22-WIP-b2e97fe0e through v0.2021.02-WIP-879ef3fe1 and tyse-v0.2021.02-879ef3fe1-regular through tyse-v0.2021.28-af66b6905-regular, are vulnerable to Host Header Injection. By luring a victim application-user to click on a link, an unauthenticated attacker can use the “forgot password” functionality to reset the victim’s password and successfully take over their account.