Since we've installed a SSL certificate on our server to improve security, with forcing https for all our sites and download, we've encountered a problem for some user's of Avast while installing our BBLog addon.
Avast have a feature called "Enable HTTPS scanning", this means that they scan and decrypt the encrypted https traffic. This feature have many "false-positive" matches. A more detailed view and workaround here:
BBLog is not the only site and service the have problems with the "special feature" from avast.
We can nothing do against this errors, the best is to just disable HTTPS scanning for the download of our addon.