Recently (probably beginning within days ago) I began to realize that my Mozilla Firefox (current ver. 39.0) browser is no longer displaying .png & .svg images (.jpg images isn't affected whatsoever) in Wikipedia articles or pages even when it is running in safe mode. However, strangely enough, Wikipedia articles or pages loaded just fine in Internet Explorer thus eliminating the issue being server-side. Attempted to reset the Mozilla Firefox browser and manually clearing away all cache and cookies even though I'm always private browsing permanently anyway but the issue persisted.
So after some diagnostic and troubleshooting, I believed I might have isolated the fault to Avast Internet Security (current ver. 10.3.2225) as Wikipedia articles or pages loaded fine with it being disabled. Is there any reason why this peculiar issue should be happening in Mozilla Firefox only, considering the configurations and setting has been as it is for months since the last time time I went through them, and most importantly, how do I resolve this?
Any help at all is deeply appreciated and a thank you in advance!