diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index a8207a4..430ae1c 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -2,3 +2,8 @@
 **Vulnerability:** Unvalidated inputs passed to `if()` statements can cause process crashes (`condition has length > 1`) or unexpected coercion vulnerabilities.
 **Learning:** In R, optional boolean parameters that default to `NULL` should be validated using explicit runtime type validation (e.g., `if (!is.null(flag) && (!is.logical(flag) || length(flag) != 1 || is.na(flag)))`).
 **Prevention:** Always implement explicit runtime type validation for optional boolean parameters.
+
+## 2024-07-16 - Fix weak regex validation in readline inputs
+**Vulnerability:** Weak regex `^[0-9]+$` on interactive inputs allowed arbitrarily large integers which R coerces to `NA` when converting via `as.integer()`.
+**Learning:** This `NA` coercion in subsequent `if` condition checks causes Unhandled Exception crashes and constitutes a Denial of Service (DoS) vulnerability. Bounded exact-match regex like `^[12]$` must be used for limited choices.
+**Prevention:** Always use bounded exact-match regex validations when accepting user inputs intended for exact menu choices.
diff --git a/R/aFIPC.R b/R/aFIPC.R
index 6254651..918e19b 100644
--- a/R/aFIPC.R
+++ b/R/aFIPC.R
@@ -141,7 +141,7 @@ autoFIPC <-
       }
       for (attempt in seq_len(3)) {
         n <- readline(prompt = "Is it correct? (1: Yes 2: No) : ")
-        if (grepl("^[0-9]+$", n)) {
+        if (grepl("^[12]$", n)) {
           return(as.integer(n))
         }
       }
@@ -171,7 +171,7 @@ autoFIPC <-
               readline(
                 prompt = "Do you want to use default BILOG-MG priors for oldform Data? (1: Yes 2: No) : "
               )
-            if (grepl("^[0-9]+$", n)) {
+            if (grepl("^[12]$", n)) {
               return(as.integer(n))
             }
           }
@@ -390,7 +390,7 @@ autoFIPC <-
               readline(
                 prompt = "Do you want to use default BILOG-MG priors for newform Data? (1: Yes 2: No) : "
               )
-            if (grepl("^[0-9]+$", n)) {
+            if (grepl("^[12]$", n)) {
               return(as.integer(n))
             }
           }
diff --git a/tests/testthat/test-autoFIPC.R b/tests/testthat/test-autoFIPC.R
index 13cecd9..8950053 100644
--- a/tests/testthat/test-autoFIPC.R
+++ b/tests/testthat/test-autoFIPC.R
@@ -89,3 +89,78 @@ test_that("autoFIPC validates input types securely", {
     "Security Error: tryEM must be a single non-NA logical value"
   )
 })
+
+library(mockery)
+test_that("interactive inputs are securely validated", {
+  mock_readline <- mockery::mock("3", "3", "3", "3", "1", "3", "3", "3", "3", "1", "3", "3", "3", "3", "1")
+  mockery::stub(aFIPC::autoFIPC, "readline", mock_readline)
+  # simulate interactive session
+  mockery::stub(aFIPC::autoFIPC, "interactive", TRUE)
+
+  # Check validation limits failure when 3 is supplied repeatedly
+  expect_error(
+    aFIPC::autoFIPC(
+      newformXData = data.frame(A=1),
+      oldformYData = data.frame(A=2),
+      newformCommonItemNames = c('A'),
+      oldformCommonItemNames = c('A'),
+      confirmCommonItems = NULL
+    ),
+    "Too many invalid common item confirmation attempts"
+  )
+})
+
+test_that("interactive inputs are securely validated for 3PL prior questions", {
+  skip_if_not_installed("mirt")
+
+  set.seed(123)
+  old_data <- as.data.frame(matrix(sample(0:1, 100, replace=TRUE), ncol=5))
+  new_data <- as.data.frame(matrix(sample(0:1, 100, replace=TRUE), ncol=5))
+  names(old_data) <- paste0("I", 1:5)
+  names(new_data) <- paste0("I", 1:5)
+
+  mock_readline <- mockery::mock("3", "3", "3")
+  mockery::stub(aFIPC::autoFIPC, "readline", mock_readline)
+  mockery::stub(aFIPC::autoFIPC, "interactive", TRUE)
+
+  expect_error(
+    aFIPC::autoFIPC(
+      newformXData = new_data,
+      oldformYData = old_data,
+      newformCommonItemNames = c('I1'),
+      oldformCommonItemNames = c('I1'),
+      confirmCommonItems = TRUE,
+      itemtype = "3PL"
+    ),
+    "Too many invalid oldform BILOG prior attempts"
+  )
+})
+
+test_that("interactive inputs are securely validated for 3PL prior questions newform", {
+  skip_if_not_installed("mirt")
+
+  set.seed(123)
+  old_data <- as.data.frame(matrix(sample(0:1, 100, replace=TRUE), ncol=5))
+  new_data <- as.data.frame(matrix(sample(0:1, 100, replace=TRUE), ncol=5))
+  names(old_data) <- paste0("I", 1:5)
+  names(new_data) <- paste0("I", 1:5)
+
+  # Suppress the mirt 1 cycle warning during the mock model generation
+  mock_old_model <- suppressWarnings(mirt::mirt(old_data, 1, itemtype = '3PL', technical = list(NCYCLES = 1), verbose = FALSE))
+
+  mock_readline <- mockery::mock("3", "3", "3")
+  mockery::stub(aFIPC::autoFIPC, "readline", mock_readline)
+  mockery::stub(aFIPC::autoFIPC, "interactive", TRUE)
+
+  expect_error(
+    aFIPC::autoFIPC(
+      newformXData = new_data,
+      oldformYData = mock_old_model,
+      newformCommonItemNames = c('I1'),
+      oldformCommonItemNames = c('I1'),
+      confirmCommonItems = TRUE,
+      itemtype = "3PL"
+    ),
+    "Too many invalid newform BILOG prior attempts"
+  )
+})