yesterday we discovered that the
display property was not properly hashed with Blockcerts v3.
We have identified the issue and patched the different libraries (blockcerts verifier still in progress at this moment).
But that implies that any cert that were issued before today have the vulnerability where someone could modify the display layer without getting noticed.
As such we advise that you invalidate and reissue certificates that were issued before today. Please update the libraries first to ensure proper propagation of the fix.