In the morning, Firefox was pleased with the warning:

It is proposed to disable Java Plug-in (what is required to run Java applets in the browser)
The explanation can be found in the FAQ on
java.com :
http://www.java.com/en/download/help/firefox_addons.xml .
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In short, it is proposed to install a new version of Java, and some .dll need to find and remove manually.
From the point of view of a normal user, this is an absolutely unacceptable solution. Non-programmers will not understand, just click OK in the window and disable Java applets.
Conclusion: the Java applet plug-in in the browser had a lot of flaws before, but now it just doesn't make sense to use applets in projects (if someone has done this before).