**Steps to replicate the issue** (include links if applicable):
version I
* if "2017 wikitext editor" is enabled, disable it (i am not familiar with 2017, never used it. it may or may not exhibit similar issue)
* open a page in source editor
* add "bla" before the first line and "bla bla" after the last (or any other easy to detect change)
* hit "Show Preview"
* hit the "Back" button of the browser
version II:
* same as version I, except replacing "show preview" with "show changes"
**What happens?**:
the page goes back to "edit source" screen, with source of original page, and all the edit changes made prior to clicking "show preview/changes" are gone
**What should have happened instead?**:
a warning should have been shown. to see the correct behavior, repeat the reproduction, but this time omit the "Show preview/changes" step.
**Software version** (skip for WMF-hosted wikis like Wikipedia):
**general comments
* possibly, likely even, this report is a dupe. i tried to find similar report and failed
* IMO, this is a show-stopper, and should be fixed before next version is released
* i do not have access to sites running older version of mw, so i cannot say if this behavior was always like this (i will be mightily surprised to hear that), and if not, when it appeared.
* i had difficulties selecting "Tags". i hope "EditNotify" is the right one. please correct it if there is more suitable project.
peace