This message looks very similar to Base64, but with different index table. With some guessing we can create new index table and map it to the standard one for decoding. 
```import base64
encoded = 'гЖзпвшБпвшБзИЗНлШ3ЙлгВБуЩЧНщШЦглИЖЩшб20жа2Ейа2ХшвщоКХ2ФжШЧЙлИЖСпв2НхгмХшЩЦРтИЖ5лгшБиШЧНлИЖЕйШ2ХщвшБцШЧНщг29шЩВБпвшБса3Н7Ш3ХщгЖ9уЧ2И2НЕ9збЗБоШЦЙлгЕ9йНЖ50ЧшС0МЗБедУБ1еР=='
alphabet = 'АБВГДЕЖЗИЙКЛМНОПРСТУФХЦЧШЩабвгдежзийклмнопрстуфхцчшщ0123456789+/'standard_base = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
encoded = encoded.translate(str.maketrans(alphabet, standard_base))decoded = base64.b64decode(encoded)
print(decoded.decode())```
This outputs: >this is a secret message from kackers:We are discovered, new base access password is kks{custom_b64_alphabet_c4nt_$t0p_y0u}
