Software developers mostly focus on functioning code while developing their software paying little attention to the software security issues. Now a days, security is getting priority not only during the development phase, but also during other phases of software development life cycle (starting from requirement specification till maintenance phase). To that end, research have been expanded towards dealing with security issues in various phases. Current research mostly focused on developing different prediction models and most of them are based on software metrics. The metrics based models showed higher precision but poor recall rate in prediction. Moreover, they did not analyze the roles of individual software metric on the occurrences of vulnerabilities separately. In this paper, we target to track the evolution of metrics within the life-cycle of a vulnerability starting from its born version through the last affected version till fixed version. In particular, we studied a total of 250 files from three major releases of Apache Tomcat (8, 9 , and 10). We found that four metrics: AvgCyclomatic, AvgCyclomaticStrict, CountDeclMethod, and CountLineCodeExe show significant changes over the vulnerability history of Tomcat. In addition, we discovered that Tomcat team prioritizes in fixing threatening vulnerabilities such as Denial of Service than less severe vulnerabilities. The results of our research will potentially motivate further research on building more accurate vulnerability prediction models based on the appropriate software metrics. It will also help to assess developer's mindset about fixing different types of vulnerabilities in open source projects.