It will be interesting to see if through CCTV or witnesses that the US military investigators will be able to track down who left the propaganda on the US bases:
U.S. Forces Korea is warning servicemembers on the peninsula to stay alert to potential insider threats after North Korean propaganda appeared on American bases.
The 8th Army reported that propaganda leaflets were discovered at Seoul’s Yongsan Garrison Thursday, shortly after a North Korean soldier defected across the heavily fortified border just north of the South Korean capital.
In an alert posted later that day on USFK’s Facebook page, officials said a significant number of North Korean propaganda leaflets and CDs had been placed at strategic locations on multiple U.S. military installations in South Korea. [Stars & Stripes]
You can read more at the link, but I would not be surprised if the propaganda was left by a sympathetic South Korean leftist with base access instead of a North Korean spy.