Moderately Critical PDF Generator API Security Advisory

This module enables you to generate PDF versions of content.

According to Drupal.org some installations of the module make use of the dompdf/dompdf third-party dependency.

Security vulnerabilities exist for versions of dompdf/dompdf before 2.0.0 as described in the 2.0.0 release notes.

Solution: 
Install the latest version:

If you use the pdf_api module for Drupal 2.x, upgrade to pdf_api 2.2.2

Source: