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I'd agree with Orange-crowned Warbler, subspecies celata ('taiga' in Sibley; as opposed to the local west-coast breeding lutescens), though that yellowish rump is odd (the yellowish under-tail coverts do fit). Slightly reminiscent of Virginia's Warbler, but that doesn't fit on other characters (e.g. has complete eye ring).
Otherwise, it looks very like a Chiffchaff (Phylloscopus collybita) from my side of things (it breeds as far east as about 145°E in eastern Siberia). But again, the yellowish rump is the sticking point. Of others from Siberia, Dusky and Radde's Warblers can be counted out, they both have much more prominent supercilia.