Avast reports untrustworthy add-ons to my Firefox browser

I am running Avast 2015.10.2.2218 with Virus definitions version 150521-0 (Number of definitions: 4,049,962).

Several times in the past 2 months I have received a message from Avast that my browser (Firefox) has suspicious add-ons associated with it. However, when I ask to see the details, it tells me there are not suspicious add-ons.

Is there a way to get Avast to stop giving me these false alarms, or is this a known bug that Avast needs to correct?

Thank you,

Victor Schwartz
victor@whyaduck.org

Hello

https://sites.google.com/site/cannedfixes/farbar-recovery-scan-tool/FRST.gif
Scan with Farbar Recovery Scan Tool

Please download Farbar Recovery Scan Tool and save it to your desktop.

Note: You need to run the version compatibale with your system. If you are not sure which version applies to your system download both of them and try to run them.
Only one of them will run on your system, that will be the right version.

[*]Double-click to run it. When the tool opens click Yes to disclaimer.
[*]Press Scan button.
[*]It will make a log (FRST.txt) in the same directory the tool is run. Please attach it to your reply.
[*]The first time the tool is run, it makes also another log (Addition.txt). Please attach it to your reply.