FreshRSS: Double clickjacking can lead to privilege escalation

FreshRSS is a free, self-hostable RSS aggregator. In versions 1.26.3 and below, due to a bypass of double clickjacking protection (confirmation dialog), it is possible to trick the admin into clicking the Promote button in another user's management page after the admin double clicks on a button inside an attacker-controlled website. A successful attack can allow the attacker to promote themselves to "admin" and log into other users' accounts; the attacker has to know the specific instance URL they're targeting. This issue is fixed in version 1.27.0.