Backdoors
"users need to create emergency plans in case FOSS contributed to in China is found to contain backdoors or security holes"?
No criticism of individual Chinese developers intended, but how do we know that there will not be, uhh, Committee pressure to add certain 'features' to libraries (carefully obfuscated in the code, various vulnerabilities have shown us that the maxim "with enough eyes, all bugs are shallow" doesn't always work)?
(Of course, the same concern may well also apply to development done in certain other countries, or under the oversight of certain large corporations...)