PHP 5.5.13 breaks backwards compatibility

There’s a backwards compatibility break in PHP 5.5.13 (and PHP 5.4.29) affecting PHPUnit, Mockery, Doctrine, Symfony and probably a lot more.
Rafael Dohms triggered me with this Tweet;

And I just ran into the issues with Mockery/PHPUnit;

Failed asserting that exception of type "PHPUnit_Framework_Error_Warning" matches expected exception "SymfonyComponentHttpKernelExceptionNotFoundHttpException". 
Message was: "Erroneous data format for unserializing 'Mockery_9_Symfony_Component_HttpFoundation_File_UploadedFile'".

I found the following sources that explain what happened:

I advise to not upgrade to PHP5.5.13 but wait for PHP5.5.14, it should be released soon.