I was searching easy-to contribute project in Google and I found a project named "Image-To-Pdf" that is an android application, and allow to the user to convert an image to an .pdf file and do a lot of transformation of a .pdf file. This project is fully written in Java.
##Contribution
I looked at the issue section of this repo and I found that there was a vulnerabilities problem, The app was using an old version (5.5.10) library named "itext" that allow to convert image to pdf. I made a change in the .gradle file and now the application is using "itext" version 5.5.13.3.
##Compiling the project and OS
I used Ubuntu OS for making this contribution and Android Studio (open-source) for compiling the project and making change.
##Communication
I was able to interact with the person who published this issue and he told me that my pull-request was perfect for fixing all of these vulnerabilities.