A bit of history, context, and what you can expect to see in articles

Back in 2012, Doc James made a query over at WikiProject Medicine about what sort of work could be done by a bot to find retracted papers. At the time, there was no centralized way of finding retracted papers, so Rich Farmbrough queried the PubMed database looking for retraction-related keywords (like 'retraction of publication' in the metadata). Of the roughly 4000 retractions, he found 138 that matched papers cited on Wikipedia. The template {{retracted}} was created to flag those papers, and was manually and semi-automatically added to articles.

Then in 2018, JenOttawa noticed the then newly-launched RetractionDatabase.org, a database of retractions maintained by Retraction Watch. This led Samwalton9 to code the first iteration of RetractionBot. The bot was then doing automatically what people did manually, saving everyone a lot of hassle. However, the bot only ran for a few months, and hit a snag: several Cochrane Reviews were flagged as retracted for technical reasons, while they were never retracted in actuality. The bot was put on hiatus, and Samwalton9 never got to fixing the issue.

Five years later, motivated by the slew of retractions hitting major publishers from Elsevier, Hindawi, SAGE, and many others, as well as the opening up of RetractionDatabase.org (now with nearly 40,000 retractions), I thought it would do us some good to kick the hornet's nest and see if I could interest someone in revisiting this project.

Turns out I could. Not even a week after probbing the volunteers at WP:BOTREQ, mdann52 graciously took over maintenance of RetractionBot, and the bot is now back alive, with many improvements. In particular, it now covers expressions of concerns, not only retractions, which are early warning signs that a paper might be dubious and could be retracted/in need of a major revision. This led to the creation of {{expression of concern}}, which works very similarly to {{retracted}} (see below).

The bot first downloads a .csv file containing all the information in the RetractionDatabase (a 50MB download available here). Then it crosschecks retracted DOIs and PMIDs in the database against those found on Wikipedia.

If a match is found, the bot will, for example, change

• ...Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.^[1]
  

to

• ...Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.^[1]
  

It is now up to humans like you to review if this is problematic for the article. If the citation is no longer reliable, then the article needs to be updated, which could be as minor as the removal/replacement of the citation with a reliable one, to rewriting an entire section that was based on flawed premises. If the citation to a retracted paper was intentional, like in the context of a controversy noting that a paper was later retracted, you can replace {{retracted|...}} with {{retracted|...|intentional=yes}}, suppressing the red notice

• ...Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.^[1]
  

If you are interested in doing systematic work involving Wikipedia articles citing retractions, the category Category:Articles intentionally citing retracted publications will be automatically populated by {{retracted}}. The retractions that haven't yet been reviewed by a human can be found in the sub-category Category:Articles citing retracted publications instead.

Otherwise? Well... carry on as usual. But if you see one of those big red notices, don't panic. Treat it like any other unreliable source, and update the article accordingly. If a retraction paper (or one with an expression of concern) is intentionally cited, then simply follow the instructions and replace {{retracted|...}} with {{retracted|...|intentional=yes}} (or {{expression of concern|...}} with {{expression of concern|...|intentional=yes}}) to suppress the red notice.

And while these are not currently handled by RetractionBot, {{erratum}} and Category:Articles intentionally citing publications with errata / Category:Articles citing publications with errata work very similarly to the above categories for papers with errata and might also be of interest to you.

Happy editing!