Incident 197: Facebook Internally Reported Failure of Ranking Algorithm, Exposing Harmful Content to Viewers over Months

Description: Facebook's internal report showed an at-least six-month long alleged software bug that caused moderator-flagged posts and other harmful content to evade down-ranking filters, leading to surges of misinformation on users' News Feed.


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Alleged: Facebook developed and deployed an AI system, which harmed Facebook users.

Incident Stats

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Sean McGregor, Khoa Lam

Incident Reports

Facebook boosted harmful posts due to 'massive ranking failure' bug · 2022

For the last six months, Facebook engineers have been seeing intermittent spikes in misinformation and other harmful content on News Feed, with posts that would usually be demoted by the company's algorithms being boosted by as much as 30% …

A Facebook bug led to increased views of harmful content over six months · 2022

A group of Facebook engineers identified a “massive ranking failure” that exposed as much as half of all News Feed views to potential “integrity risks” over the past six months, according to an internal report on the incident obtained by Th…

Facebook system designed to smother harmful misinformation actually spread it · 2022

Facebook engineers have belatedly uncovered a significant flaw in its downranking system to filter out harmful content, which exposed up to half of all News Feed views to potential ’integrity risks’ for six months.

Reports in The Verge sugg…

Meta admits Facebook bug led to a 'surge of misinformation' · 2022

Meta has admitted that a Facebook bug led to a 'surge of misinformation' and other harmful content appearing in users' News Feeds between October and March.

According to an internal document, engineers at Mark Zuckerberg's firm failed to su…


A "variant" is an incident that shares the same causative factors, produces similar harms, and involves the same intelligent systems as a known AI incident. Rather than index variants as entirely separate incidents, we list variations of incidents under the first similar incident submitted to the database. Unlike other submission types to the incident database, variants are not required to have reporting in evidence external to the Incident Database. Learn more from the research paper.