Yes, targeted attacks like that definitely exist, most famously maybe the most recent social pressure to merge a vulnerability to the xz library by actor "Jia Tan":

https://arstechnica.com/security/2024/04/what-we-know-about-the-xz-utils-backdoor-that-almost-infected-the-world/

This started a whole discussion about relying on (often unpaid) volunteer work for critical systems and the pressure and negativity these people face, which is a discussion that was absolutely needed, and which we are still lightyears away from fixing.

Currently, open source is still treated like this: https://trac.ffmpeg.org/ticket/10341

(I can only recommend reading the whole story around this issue, which boils down to Microsoft admitting they rely on an open source project for something they consider critical to their customers, but not willing to pay the maintainer a bounty for fixing the issue)

[–] teawrecks@sopuli.xyz 6 points 4 months ago

The NSA is doubtless sitting on a trove of these types of vulnerabilities to use when they really need access to something.