Reposting this from site stuff and chat as here is where a lot of reporting of posts happens
www.mumsnet.com/talk/site_stuff/4564026-change-in-format-of-response-to-report-emails
www.mumsnet.com/talk/_chat/4564131-another-mumsnet-data-breach
We had a temporary glitch with 'Report this post' for a short time today which meant the email of the person reported was included in the report and in a few cases in responses to those reports. This applies to a very small number of users and we'll be contacting them shortly to let them know. Our DPO has been informed and on his advice we'll report it the ICO if appropriate. Please be assured the issue is now fixed. We will of course be examining how it happened to ensure it never happens again. We're really sorry for any concern caused.