The plugin does not validate the submitted rating, allowing submission of long integer, causing a Denial of Service in the review section when an authenticated user submit such rating and the reviews are set to be displayed on the post/page
Proof of Concept
Enable reviews for post/pages, and enable the "Show Reviews on" setting for All posts or pages as well.
Then log in as a user such as subscriber and submit a review with a long rating, e.g
POST /wp-comments-post.php HTTP/1.1
Accept-Encoding: gzip, deflate
The review section of the post/page will crash with an error like "Allowed memory size of 268435456 bytes exhausted (tried to allocate 249561152 bytes) in /var/www/wp-content/plugins/reviews-plus/functions/functions.php on line 76" when viewed