[Clamsoda]

Dry coded, untested. I am not sure what the arguments are for TargetFrame_UpdateAuras, they could help in optimizing the code; I am also unsure as to how "not s.maxBuffs or i<=s.maxBuffs" was intended to help, it seems a bit useless, but I left it.

local _, playerClass = UnitClass("player")
if (not playerClass == "ROGUE") then return end
 
local spellIDs = {
    49016 = true,
    52610 = true,
    5229  = true,
    34692 = true,
    19574 = true,
    18499 = true
}
 
hooksecurefunc("TargetFrame_UpdateAuras", function(self)
    for i = 1, MAX_TARGET_BUFFS do
        local _, _, icon, _, debuffType, _, _, _, _, _, spellID = UnitBuiff(self.unit, i)
 
        if (icon) and (not self.maxBuffs or i <= self.maxBuffs) and (spellIDs[spellID]) then
            local stealableBorder = _G[self:GetName().."Buff"..i.."Stealable"]
 
            if UnitIsEnemy("player", "target") and (debuffType == "Magic") then
                stealableBorder:Show()
            else
                stealableBorder:Hide()
            end
        end
    end
end)