Users that had been using Facebook or Google identities to use Yahoo services will need to revert to Yahoo ID as the company begins phasing out support for the login alternatives across its service portfolio.
First reported by Reuters, the reversal began with the Yahoo Sports Tourney Pick'Em service earlier this week, before extending to more popular services such as Flickr and other Yahoo Sports brands. No timeline is set for these services to forgo compatibility with other identity providers.
A spokesperson for the company said that asking users to sign up using a Yahoo ID would allow Yahoo to "offer the best personalized experience to everyone".
One of the last major changes that the company made, a visual update of its Yahoo Mail service, was met with howls of derision from its user base when the removal of interface features was paired with a service outage resulting in failed email delivery issues for two and a half weeks.
Earlier this year, the company finally enabled HTTPS by default for its userbase of over 200 million people.
Also in January, a malware attack aimed Yahoo's European users from its ad network attempted to construct a bitcoin mining network. The malware exploited vulnerabilities in outdated Java installations.
Last week, it was revealed that Britain's chief spy agency, the GCHQ, and the United States' NSA had collected webcam imagery from millions of users of Yahoo's Messenger service.
Yahoo "strongly condemned" and denied any complicity in the program, dubbing it a "whole new level of violation of our users' privacy".
In all, the program collected imagery from more than 1.8 million Yahoo user accounts globally. Images were captured up to once every five minutes, with quicker capture avoided to prevent overloading the systems of GCHQ. As much as between 3 percent and 11 percent of the snapped imagery was considered "explicit", and was collected via taps on intercontinental submarine cables.