In the past few days, webmasters have been reporting in various forums that they have witnessed significant traffic changes with the epicenter being around September 9th.
This correlates with some form of September update, with travel and tourism websites reporting changes on and around September 7th.
Some forum users are reporting a potential glitch:
Today all projects have lost 90%, even blogs with unique content – a glitch?
One common theme amongst the comments is the focus around content quality and uniqueness, with most webmasters speculating this update has been a refresh of the AGS filter.
According to Plato Shchukin:
We are carrying out technical work to improve the performance of search algorithms and further expand our search base. This may lead to temporary changes in the number of pages in the search base. We are making sure that this update does not affect the traffic that the site receives from search.
So this could be both an algorithm update, and slight technical glitch.