default browser settings in Thunderbird changed by updates overnight

[Claude Jones]

Clicking an html link from within a Thunderbird message now opens 
Chrome. It has been set to Firefox for a long time. This appears to have 
changed since yesterday, and last night I did run a huge number of new 
updates.

Funny thing is, the settings in about:config in Thunderbird still 
dictate firefox as the preferred browser:

network.protocol-handler.app.ftp;/usr/bin/firefox
network.protocol-handler.app.http;/usr/bin/firefox
network.protocol-handler.app.https;/usr/bin/firefox

Checking "System settings\Default Applications\web Browser" (in KDE) 
also shows Firefox configured as default browser

Where else can this behavior be controlled. I would like to know which 
package update caused this behavior to change so I can file a bug 
report, but I'm not sure. Looking at the long list of updates last 
night, there were updates for both Firefox and Thunderbird, but not for 
Chrome. I can't imagine Thunderbird changing the defaut browser to open 
from links, and the settings still seem correct.

Ideas?
-- 
Claude Jones
Brunswick, MD, USA