|This page summarizes an issue affecting Wikimedia sites relating to some client-side third-party ad blocking filter that caused some pages in some user's browsers to appear blank when an 'EasyList' filter list was installed and used by users in their web browsers. It is being done by User:RhinosF1 with User:BWolff (WMF) assisting on some statistics.|
On the 4th April 2019, a report was received that the ads page on English Wiktionary was not displaying content for a user via 'Grease Pit'.
It was determined at 13:13 UTC that this was down to an ad blocker being overly zealous with multiple users confirming issues over the coming minutes including it now affecting the Advert Page and German Wiktionary
Investigations continued with a customer support query being filed with AdBlock at 13:29 UTC which was later withdrawn as more information became available,
As users continued to look into it Lucas (WMDE) identified that it was down to a component of multiple ad blockers known as 'EasyList' which had had added a rule matching the pages on the 4th September 2018. 
Shortly after a bug report was filed to EasyList  which led to Wiktionary domains being whitelisted at 14:43 UTC.
A message was then sent out to wikitech-l  asking that all Wikimedia sites be whitelisted with a pull request being filed on GitHiub at 18:02 UTC  which was declined with only Wikipedia domains being added in addition.
- 06:19 - A report is filed to enwikt's 'Grease Pit' claiming the ads page is not showing content.
- 06:19 - Another user mentions whether an adblocker causes it (this receives no response)
- 13:09 - A user joins the -tech IRC and reports this
- 13:12 - A users in -tech confirms the issue and states content was retrieved by browser though
- 13:13 - WMDE user states they believe it is a issue with an overly zealous CSS rule - Unable to identify where from
- 13:17 - Lucas (WMDE) states that is believed to be part of a 'uBlock Origin' Extension
- 13:19 - Issue with a 'EasyList' component is identified
- 13:29 - Issue with adblock opened - The tool RhinosF1 is using to block ads
- 13:52 - Post confirming issue is made to Wiktionary Information Desk
- 14:18 - Issue with EasyList is filed
- 14:43 - Fix for wiktionary domains is rolled out by EasyList
- 15:09 - Email sent out asking if someone would deal with EasyList whitelisting the domain
- 19:02 - Quiddity files Pull Request on EasyList GitHub Page that would whitelist Wikimedia domains
- 8 April 2019 10:00 - EasyList blocked addition of all wikimedia sites allowing only Wiktionary and Wikipeida
- Time from first report to issue being identified: 7 hours
- Time from issue being identified to bug report being filed: 59 mins
- Time from first report to bug report being filed 7 hours 59 mins
- Time from bug report to fix for specific pages on wiktionary: 25 mins
- Time from first report to fix for specific pages on wiktionary: 8 hours and 24 mins
- Time from pull request to cover all Wikimedia wikis to pushed: N/A
- Time from first report to creation of a pull request affecting all wikimedia sites: 13 hours and 43 mins
- Time from first report to fix which covers all Wikimedia wikis: N/A
- Estimated number of pages matching filter across all wikis: 26 910  - Although, as most URLs force the first letter to be uppercase - This many reduce that number. The issue has not been reported since or on non-wiktionary wikis