I received two pull requests for two of my projects on GitHub today. I am the author of one and the maintainer of the other.
At first, the pull requests did not make sense at all. One of them made minor changes to a README, e.g., changing "this book" to "the book". It did not fix a typo or grammatical error. It merely chose a word different from the one I had chosen. In fact, I preferred "this book", so the pull request (PR) was inconsistent with my preference. There was no explanation whatsoever regarding why this change was warranted. Then I looked at the pull request author's profile and found that the same person had submitted several such trivial pull requests to other projects too, all of them changing "this" to "the" at some places in various README files.
It all began to make sense when I looked at the calendar. It was Oct 01. This looked like pull request spam due to Hacktoberfest. For now, I just labelled the pull requests as "invalid" (as suggested by the Hacktoberfest FAQ), closed the pull requests, and moved on.
Like all good things created with good intentions on the Internet, spam is hurting this event and bringing bad reputation to it. The possibility of large scale, endless spam should be worked into the design of any new Internet-based event or solution.