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Firefox uses an outdated version of flashplayer. Using other applications , such as Chrome, Chromium+pepperflash, Opera+pepperflash and others...

"Using other applications" or other os)))

The Firefox version will always be outdated in features compared to pepper flash current version 21 series.
The current version of flash player for Firefox is 11.2.202.577 What is currently provided in the Deepin store gives version 11.2.202.569

Same as Firefox but more up to date, Debian's Iceweasel might be a better option. I prefer it:

Be Advised that Debian is discontinuing the Iceweasel project and is being replaced by Firefox ESR.

Indeed. And if you installed iceweasel it will automatically upgrade to firefox ESR from debian sid/unstable. Firefox (no-ESR) will also be available from debian sid/unstable in the coming days. No word on icedove/thunderbird yet but it should follow the same path soon.

All this has little to do with twoguntom's issue and topic of this post. He is well aware of alternative browsers, that has been covered in detail in one of twoguntom's  previous threads. The fact still remains there is a security update to Adobe flash version that is supplied in the Store for NPAPI browsers. Hopefully it will be in the next push of updates from Deepin.

As for Firefox, Adobe decided not to support the open-source community of Linux (has to do with some marketing business with Chrome), so they no longer release updates for Linux/Firefox. There is an easy workaround though:
https://peterpap.net/index.php/Install_Pepper_Flash_for_Firefox7

Many of the new sites no longer use streaming flash content. Eventually Adobe will stop providing security updates for the firefox version and Google will stop supporting pepper flash. Fresh player is in the repositories no need for firefox 7 information. But in my opinion, freshplayer does not work that well.
browser-plugin-freshplayer-pepperflash