Disclaimer: this post is by no means legal advice. If unsure, please seek professional consultation.
What is GDPR?
The General Data Protection Regulation (GDPR) is a legal framework that sets guidelines for the collection and processing of personal information of individuals within the European Union (EU).
Read the full definition on Wikipedia.
Does GDPR Affect Me and My Website?
If your company is based in the European Union (EU), or you do business with EU citizens, the GDPR does affect you and your website so you need to comply. With that said, it would be a good idea to comply with the regulations regardless, as it’s possible countries outside of the EU will implement similar legislation in the future.
WP Review Slider Pro Plugin
The main concern with the WP Review Slider plugin is the storing and displaying of personally identifiable information. The plugin downloads the review text, the reviewers name (or username), date, star rating, and user avatar (only if caching is turned on) of each review and stores it on your server in your WordPress database.
Remember it is up to each site to understand and comply with GDPR if needed.