Confirmed Non-atomic SVG sprite writes can cause corrupted CDN-cached icons

[Painbaker]

Affected version

2.3.13

XF writes icon sprite files directly. If the file is requested while it is being regenerated, the server can return an incomplete SVG, which may then be cached by the CDN and break icons

SpriteGeneratorService::generateForVariant() uses file_put_contents() without atomic file replacement allowing partially written files to be served