After updating to Magento 18.104.22.168 the below mentioned issues cannot install any extension from connect manager:
Unknown cipher in list: TLSv1 failed error.
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I experienced the same problem when trying to use the command line to perform updates.
I was able to fix this by commenting out line 377 of downloader/lib/Mage/HTTP/Client/Curl.php
/** Commented out to fix TLSv1 Failed Error * $this->curlOption(CURLOPT_SSL_CIPHER_LIST, 'TLSv1'); */
I do not have a good explanation to give, but this seems to work.
in the worst case, if you want immediate solution , Alternatively you can install the extension through FTP (like FileZilla). You can paste the extension key in this unofficial link and you can download the extension files. Let me know if you find any problems in this.
Note : As this is unofficial 3rd party site, there is no guarantee about security