As a part of the security updates, has made a change to the delimiters in the response transaction. This change impacts many Magento 1 online stores, as the base Magento code was unable to properly process. This change went live on Tuesday, January 22, 2019. See more information on this topic on Authorize.net at: https://community.developer.authorize.net/t5/News-and-Announcements/Changes-to-Supported-Characters-Jan-22-2019/td-p/65435
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