I have been using a ZXP InDesign extension for many years across versions CS5 and CS6.
I have just installed CC 2015 and I cannot install my InDesign ZXP extension. It tells me that the ZXP file doesn't contain a valid signature and the extension will not be installed.
Is there a way around this? The website/user of the person I downloaded it from doesn't exist anymore so assume that any sort of update will not happen.
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