懵逼 is easily construed as dirty with it's 逼 suffix. I cannot, for certain, tell if 逼 is a substitute for 屄 or not.

[Baidu Baike](https://baike.baidu.com/item/%E6%87%B5%E9%80%BC/19673061?fr=aladdin) gives no indication that it's a curse word.

But [懵X](https://www.baidu.com/s?wd=%E6%87%B5X&rsv_spt=1&rsv_iqid=0x9960830800023d36&issp=1&f=8&rsv_bp=0&rsv_idx=2&ie=utf-8&tn=baiduhome_pg&rsv_enter=1&rsv_sug3=1&rsv_sug2=0&inputT=187&rsv_sug4=188) brings up almost four million results on Baidu & 懵屄 has it's own fair-share of results.

Could it just be a happy coincidence?