censor.js

const censor = text => {
  const iter = document
    .evaluate(`//*[contains(text(),'${text}')]`, document, null, XPathResult.ANY_TYPE, null)

  let el = iter.iterateNext()
  
  while(el) {
    el.style = "color: transparent; text-shadow: 0 0 5px rgba(0,0,0,0.5);"
    try { el = iter.iterateNext() } catch (_) { break }
  }
}

const observer = new MutationObserver(() => censor('text_to_censor'))

observer.observe(document.body, { childList: true })