Several days ago to a week or two ago, I began experiencing the odd issue of seeing my posts being duplicated on LinkedIn.

Even more bizarre, was that my Twitter posts were being duplicated as well, and since I linked my Twitter account to my Facebook account, these duplicated posts were appearing on Facebook. The LinkedIn postings were being duplicated, like so:

Since my LinkedIn updates were being sent to Twitter, the first thing I did was to disable sharing of my LinkedIn updates to Twitter, and that stopped the Twitter and Facebook duplicates.

After several days of having the duplication problem, I started thinking that LinkedIn had a problem, and I created a support case with LinkedIn

.

LinkedIn Support was professional, however, they couldn't reproduce the issue.

At LinkedIn Support's suggestion, I switched browsers to Chrome and an older version of Firefox, and the duplicate postings didn't occur. This made me suspect that the Firefox Nightly I was using had a problem.

It's time to call in the tools! I used Fiddler, the HTTP Debugging Proxy, written by Eric Lawrence. Fiddler2 is a tool that can monitor all HTTP traffic sent by any browser, or any process.

One of the things I looked for was the HTTP traffic generated, when I posted.

Fiddler shows that the older Firefox browser sent a HTTP POST. When I used the Nightly version, Firefox sent 2 HTTP POSTs. So, the bug was definitely caused by Firefox Nightly.

Shortly after I discovered this issue, the Mozilla team fixed the Firefox Nightly browser, and I'm back to using it again.