While prior studies have explored security in code generated by ChatGPT and other Large Language Models, they were conducted in controlled experimental settings and did not use code generated or provided from actual developer interactions. This paper not only examines the security of code generated by ChatGPT based on real developer interactions, curated in the DevGPT dataset, but also assesses ChatGPT's capability to find and fix these vulnerabilities. We analysed 1,586 C, C++, and C# code snippets using static scanners, which detected potential issues in 124 files. After manual analysis, we selected 26 files with 32 confirmed vulnerabilities for further investigation. We submitted these files to ChatGPT via the OpenAI API, asking it to detect security issues, identify the corresponding Common Weakness Enumeration numbers, and propose fixes. The responses and modified code were manually reviewed and re-scanned for vulnerabilities. ChatGPT successfully detected 18 out of 32 security issues and resolved 17 issues but failed to recognize or fix the remainder. Interestingly, only 10 vulnerabilities were resulted from the user prompts, while 22 were introduced by ChatGPT itself. We highlight for developers that code generated by ChatGPT is more likely to contain vulnerabilities compared to their own code. Furthermore, at times ChatGPT reports incorrect information with apparent confidence, which may mislead less experienced developers. Our findings confirm previous studies in demonstrating that ChatGPT is not sufficiently reliable for generating secure code nor identifying all vulnerabilities, highlighting the continuing importance of static scanners and manual review.