In The Unicode Standard, Cyrillic script implementation is discussed in  Chapter 7 European Alphabetic Scripts.

The Cyrillic script was first encoded in The Unicode Standard version 1.0. Since that time the encoding has undergone a number of modifications; the script is now encoded in the following blocks:

Blocks Character Range Added in Unicode Version Documentation
Cyrillic 0400..04FF 1.0  U0400.pdf
Cyrillic Supplement 0500..052F 3.2  U0500.pdf
Cyrillic Extended-A 2DE0..2DFF 5.1  U2DE0.pdf
Cyrillic Extended-B A640..A69F 5.1  UA640.pdf

Subsequent to version 1.0, the following characters have been added to the Cyrillic script:

Characters Unicode Version Documentation
0400 3.0  
040D 3.0  
0450 3.0  
045D 3.0  
0487 5.1  n3194.pdf L2/07-003
0488..0489 3.0  n1744.pdf L2/98-211
048A..048B 3.2  
048C..048F 3.0  n1744.pdf L2/98-211
04EC..04ED 3.0  n1744.pdf L2/98-211
04C5..04C6 3.2  n2173 L2/00-082
04C9..04CA 3.2  n2173 L2/00-082
04CD..04CE 3.2  n2173 L2/00-082
04CF 5.0  n2942.doc
04F6..04F7 4.1  n2560.pdf L2/02-452
04FA..04FF 5.0  n2933.pdf L2/05-080R
0500..050F 3.2  n2224.pdf L2/00-182
0510..0513 5.0  n2933.pdf L2/05-080R
0514..0523 5.1  n3194.pdf L2/07-003
0524..0525 5.2  n3435.pdf L2/08-144
0526..0527 6.0  n3481.pdf L2/08-182
2DE0..2DF5 5.1  n3097.pdf L2/06-172
2DF6..2DFF 5.1  n3194.pdf L2/07-003
2E3A 5.1  n3194.pdf L2/07-003
A640..A65F 5.1  n3194.pdf L2/07-003
A660..A661 6.0  n3563.pdf L2/09-020
A662..A673 5.1  n3194.pdf L2/07-003
A674..A67B 6.1  n3748.pdf L2/10-002
A67C..A697 5.1  n3194.pdf L2/07-003
A698..A69B pending   n3772.pdf L2/09-310R
A69F 6.1  n3748.pdf L2/10-002

Documentation refers to  ISO Working Group and Unicode proposals