This happens when upgrading from Chrome 55 to Chrome 56 (56.0.2924.87).
This is an increase in security.
This does not disappear by restarting the browser, and this is not an error.
Mountain View says it hopes you will never come across a message because certification authorities should stop issuing SHA-1 certificates in 2016. Just in case, Google plans to continue issuing a warning until Chrome stops supporting SHA-1 on January 1, 2017. When this day arrives, a website that still uses the function will result in a fatal network error. (Source: Engadget.com )
If this happens, the most likely reason is that your (or website) SSL certificate uses SHA1.
SHA1 is corrupted, and SSL certificates using SHA1 are no longer protected (Chrome has now shown you this, now it blocks NET::ERR_CERT_WEAK_SIGNATURE_ALGORITHM ).
Another possible reason is that your SSL certificate has expired
In addition, you must disable backward compatibility with SSL2 and SSL3 ( Poodle Attack ).
You should use only TLS (SSL 3.1+).
To test the SSL domain certificate, you can use the SSL SSL test SSL .
To find out what the problem is: Open the Chrome Developer Console (CTRL + SHIFT + J OR F12) and go to the security tab



For more information:
https://support.google.com/chrome/answer/95617?visit_id=1-636221396724527190-3454695657&p=ui_security_indicator&rd=1
FYI:
Over the course of a decade, SHA-1 has become weaker and more insecure now it is dangerous because we tend to trust websites with "https: //" in our URLs. Other browsers, such as Mozilla Firefox and Microsoft Edge, also plan to end support in encouraging website owners to secure SHA-2 certificates as soon as possible.
If you urgently need to get around this (you need to close all running instances of Chrome first - otherwise it will not work ):
chrome --args --ignore-certificate-errors
Please note: do not do online banking or gmail with these command line options that are active in your Chrome instance.
Stefan Steiger Feb 08 '17 at 8:40 2017-02-08 08:40
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