Implement The most PCI compliant Plugin possible.

Note that using 3D secure (or similar strong authentication) becomes a legal requirement by 2019 if you have any European customers.

So would be nice if it was implemented before then.

For recurring transaction it is sufficient to apply it in on first charge.

http://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32018R0389&from=EN

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Article 14

Recurring transactions

1. Payment service providers shall apply strong customer authentication when a payer creates, amends, or initiates for the first time, a series of recurring transactions with the same amount and with the same payee.

2. Payment service providers shall be allowed not to apply strong customer authentication, subject to compliance with the general authentication requirements, for the initiation of all subsequent payment transactions included in the series of payment transactions referred to in paragraph 1.

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(While it says "payment service providers", they will delegate those requirements to you if you accept cards on your own site)

I am also for Blesta to support the new functions introduced by Stripe.

At least the essentials so that we no longer have to Process payments unsafely.

According to https://docs.blesta.com/display/user/Stripe

Stripe Elements and 3D Secure is the primary blocker to me from moving to Blesta.

Please add support for 3DS

September 2019 is the date we have to be compliant in this - Payment declined notices will be issued for those that cannot be authenticated using the new API

This has been completed in 4.7.0.