The ABP Support Team (Shannon and/or Jessy) has been reporting since yesterday the steps to follow to recover the functionality of the blocker and other add-ons installed in our Firefox ... you just have to follow its instructions and the problem is solved.

Many thanks to the ABP Support Team for their dedication and the Mozilla Technical Team for quickly implementing a patch for this bug.

Write "about:config" in adress bar and set "xpinstall.signatures.required" to false