Checked issue and is reproducible in all Os and all versions Windows10 64bit, Ubuntu 18.04 64bit and macOs 10.15 Using firefox Release 77.0.1, Beta 78 and Nightly 79.0a1 - launch firefox - https://addons.mozilla.org/en-US/firefox/addon/add-custom-search-engine/ - in addon , add search "biin," and link "https://www.bing.com/search?q=selenium" - go to about:preferences#search - Uncheck "biin," from one click engines - refresh page> biin, becomes checked again.
Bug 1643887 Comment 3 Edit History
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Checked issue and is reproducible in all Os and all versions Windows10 64bit, Ubuntu 18.04 64bit and macOs 10.15 Using firefox Release 77.0.1, Beta 78 and Nightly 79.0a1 - launch firefox - install addon https://addons.mozilla.org/en-US/firefox/addon/add-custom-search-engine/ - in addon , add search "biin," (it has a comma at the end), and link "https://www.bing.com/search?q=selenium" - go to about:preferences#search - Uncheck "biin," from one click engines - refresh page> biin, becomes checked again.