Finally, the English version of “JavaScript prototype pollution: practice of finding and exploitation” article is prepared. Using the techniques Nikita Stupin discovered CVE-2020–28460 in multi-ini parser and a vulnerability in the merge-deep package. With the first one, everything went smoothly, but with the second one, a funny situation came out: after sending the report, the maintainer did not get in touch for a long time, and as a result, GitHub Security Lab found the same vulnerability, managed to reach the maintainer earlier and registered it (GHSL-2020–160). All details related to these vulnerabilities, discovery and exploitation techniques, and recommendations on how to protect your applications are collected in the article.