Rulings
Q1: What happens to cards placed face up in the security stack by effects?
They become face-up security cards that remain revealed. Other than rules that specify face-up security cards, the rules apply in the same manner as standard security cards.
Q2: What happens upon a security check for a security card that is placed face-up?
The check is performed with the card left revealed. Other than rules for cards left revealed, the rules apply in the same manner as standard security checks.
Q3: Does a card's Security effect trigger upon a security check with that card placed face-up?
Yes, it triggers.
Q4: What happens if I shuffle a security stack that includes security cards placed face-up?
Any face-up cards are placed face down, then you shuffle the cards. After shuffling, all cards are left face-down.
Data Sources
Hornet Eraser BT19-096 C Royal Base/LIBERATOR [Main] You may place 1 Digimon card with the [Royal Base] trait from your trash face up as the bottom security card. Then, delete up to 8 play cost's total worth of your opponent's Digimon. For each of your face-up security cards, add 2 to this effect's play cost maximum. --- [Security] Activate this card's [Main] effects.
Hornet Eraser BT19-096 C Royal Base/LIBERATOR [Main] You may place 1 Digimon card with the [Royal Base] trait from your trash face up as the bottom security card. Then, delete up to 8 play cost's total worth of your opponent's Digimon. For each of your face-up security cards, add 2 to this effect's play cost maximum. --- [Security] Activate this card's [Main] effects.
Hornet Eraser BT19-096 C Royal Base/LIBERATOR [Main] You may place 1 [Royal Base] trait Digimon card from your trash face up as your bottom security card. Then, delete up to 8 play cost's total worth of your opponent's Digimon. For each of your face up security cards, add 2 to the maximum play cost you may choose with this effect. ---
ホーネットイレイザー BT19-096 C ローヤルベース/リベレイター 【メイン】自分のトラッシュから、特徴に「ローヤルベース」を持つデジモンカード1枚をセキュリティの下に表向きで置ける。その後、登場コスト合計8まで、相手のデジモンを消滅させる。自分の表向きのセキュリティ1枚ごとに、この効果の登場コスト上限+2。 --- 【セキュリティ】このカードの【メイン】効果を発揮する。