I woke up this morning to find a ton of randomly-named files in the root directory of several of my WordPress installations. The files are named similarly to 0303c831c9c6203ba966dbf523d119ab.dat. The data of these files looks like a serialized PHP value.
I’m not sure if these files are due to the upgrade I performed to WordPress 3.0.1 last night, though they seemed to begin appearing shortly after I applied that upgrade. I’m speculating that they’re due to the way one of my plugins – perhaps Hyper Cache – is interacting with 3.0.1. It’s either that or some malicious infection. Either way, I’ll update here when I find out what’s causing it.
Have you noticed extra, random files in your WordPress installation after upgrading to 3.0.1? If so, hit the comments.
UPDATE: It looks like I can confirm that the problem was due to the Hyper Cache plugin. Upon automatically upgrading to the latest version of the plugin, 2.7.3, WordPress complained that it couldn’t find a cache directory and instructed me to create that directory. Even though I did, it seems it was still storing the cache files – these mysterious .dat files – in the WordPres root directory. After deactivating and reactivating the plugin, it seems to be storing the cache files in the correct location now.