Google announced the November 2021 spam update on 3rd Nov 2021 with its standard wording: "As part of our regular work to improve results, we've released a spam update to our systems". It added that it "should be fully rolled out within a week", per Search Engine Land's coverage.
On 11th Nov Google confirmed "This update is complete". Its ranking updates history logs the rollout at 8 days 1 hour, close to schedule.
Google did not say which spam techniques the update went after. Search Engine Land reported it appeared to be about content spam rather than link spam.
Link spam was ground the July 2021 link spam update had covered four months earlier. Search Engine Land also noted that only sites engaged in tactics the algorithm targeted would have felt it.
If rankings fell in the 3rd to 11th Nov window, treat it as a spam-policy problem. It is not a content-quality one.
Audit the site against Google's spam policies and remove whatever violates them.
Per Google's spam updates documentation, improvement then depends on its automated systems learning "over a period of months" that the site complies.
