According to Kim Dotcom [0] The Chinese government has a backdoor to MEGA.nz.
[0]: https://nitter.net/KimDotcom/status/1539426611870986240
[0]: https://nitter.net/KimDotcom/status/1539426611870986240
Based on the assumptions I have about MEGA, Chinese intelligence and their motivations I find it unlikely they have an active, mutual conspiracy (impractical, expensive).
I assume MEGA is as viable target for covert, low-cost try-your-luck attacks as much as any other western infrastructure/enterprise. In that sense and in this post-Snowden world we live in, it seems as likely that any capable nation or five-eyes member et.c. could have* such a "backdoor".
*edit: 'has' → 'could have'
But yeah, I don't trust mega either.